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Cameron's Coaching Corner Volume 2

Welcome to Cameron's Coaching Corner, where we answer questions from readers about leadership, career, and software engineering.

In this week's post, we look at how Chase can balance writing the perfect code and shipping something.

My question: As a young developer, I notice that sometimes I get paralyzed by options. I want to write the perfect piece of code. This helps me in writing good code but usually at the cost of efficiency. Especially when I am faced with multiple good options. Sometimes I want to KNOW I’m gonna write the right thing before I’m writing it when I my be better off with some trial and error

  1. Are these common problems that you see people face?
  2. What rules of thumb or other pieces of advice do you have to avoid writing nothing instead of something as a result of seeking the ideal?
  3. How important is planning vs trial and error ("failing fast" as they say) to good software development flow?

Five Minutes at Five Guys - When Metrics Conflict with UX

In a recent post, I spoke about the flaw of using a single metric to tell the story and how Goodhart's Law tells us that once we start measuring a metric, it stops being a useful metric.

Let's look at a real-world example with the popular fast food chain, Five Guys.

All I Wanted Was a Burger

Five Guys is known for making good burgers and delivering a mountain of piping hot fries as part of your order. Seriously, an order of small fries is a mountain of spuds. Five Guys make their fries to order, so they're not sitting around under a heat lamp.

Yo Dawg, I heard you wanted fries, so I put fries in your fries

This approach works great when ordering in person, but what happens if you order online? The process is essentially the same, the crew works on the burgers, but they won't start the fries until you're at the restaurant, so they're always guaranteeing that you get fresh made fries.

At this point, it's clear that receiving a mountain of hot, cooked-to-order fries is part of the experience and what customers expect, right?

Cameron's Coaching Corner - Mentoring an Intern

Welcome to Cameron's Coaching Corner, where we answer questions from readers about leadership, career, and software engineering.

In this week's post, we look at how test123 can improve the mentoring experience for their new intern.

I recently had an intern join my time and I’m going to be his mentor. I’ve had interns in the past, but this one doesn’t understand any fundamentals and struggles with everything.

My question to you is this, how can I help him? He doesn’t know HTML/CSS/JS, so I’m trying to teach him those, but it’s taking away a lot of time. I suggested for him to watch some videos and then we can sync twice a day to go over the topics and discuss them further.

My issue: I don’t want to just say “go watch videos.” Bc, that’s not the best way to learn - I want him to dive into the code and try things and break, that’s how I learned at least.

How do you think I should handle this? I wanna be a good mentor and I want him to learn and grow. I don’t wanna fail the kid bc I don’t know the proper way to mentor.

The Humble Function - Foundation to Functional Programming

When learning about functional programming, you won't go far before you run into the concept of a function. But we're not talking about some syntax or keywords in the language, but from a mathematical sense.

A function is a mapping between two sets such that for every element in the first set, it's mapped to a single element in the second set.

Since a set is a collection of elements, this is similar to a type where values are part of that type. With this understanding, we can modify our definition of a function to be:

A function is a mapping between two types such that for every value in the first type, it's mapped to a single value in the second type.

So What Does a Function Look Like?

Before diving into code, let's build up our understanding of functions more. When drawing out the function, we can model it like this.

Generic mapping from A to B

Generic mapping from A to B

The first type (A) is a circle where each possible value is listed, using ... to denote a pattern. The arrows map from each value of A to a value in B.

With this example, we know we have a function if the mapping satisfies the following rule:

Every element on the left maps to a single element on the right.

This rule seems easy enough to follow, but let's look at a mapping where this rule doesn't hold.

Functional Heartbreak

Let's say that we needed to write some code that could take a given month and return the number of days it has. Given this, here's what the mapping would look like.

Days in Month Mapping

Mapping from month name to days in month

To check if we have a function, we need to see if there's any element on the left with two or more arrows coming out.

In this case, February is breaking our rule because it could map to 28 or 29, depending on if it's a leap year. Since there isn't a parameter to denote if it's a leap year, our mapping isn't consistent and can't be a function.

One way to fix this would be to change our type on the left from MonthName to MonthName and year. Making this change gives us this new mapping.

Days in Month Mapping with Month Name and Year

Month and year mapping to days in month

Hip to Be Square

Let's look at a mapping that is a function, the square function.

Square mapping from number to number

Square mapping from number to number

Does every value on the left map to a single value on the right?

Yep, every value does. In fact, there are some values on the left that map to the same value on the right, which isn't a problem.

If we wanted to, we could restrict the type on the right from number to non-negative number, but there's no harm in having it be wider than needed.

Kinds of Functions

With this understanding of functions, let's talk about the two kinds of functions we can write and how they interact with each other.

Pure Functions

First, we have the pure function. These functions depend wholly on their inputs and they do not interact with outside state. For example, pure functions won't interact with databases, file systems, random generation, or time.

Pure functions are great because they're easy to test, composed with other functions, and don't modify state. Another advantage is that pure functions can be replaced with the result of their call (in other words, you could replace a call to square(3) with its result, 9 and the program is the same). This is known as referential transparency and is a great tool for troubleshooting an application.

The main downside to pure functions is that since they don't talk to other systems (including input/output), it's impossible to write a useful program with just pure functions.

Impure Functions

Impure functions, on the other hand, focus on interacting with outside state. These functions will call to the database or other systems, get the time, and generate random data as needed.

They allow us to write useful programs because they interact with input/output, however, the trade off is that they can be harder to test, they don't compose, and since they modify state, you may not be able to run them multiple times and get the same result.

One way to identify an impure function is by looking at its type signatures. For example, a function that takes inputs but returns void has to be modifying state or talking to another system, otherwise, why would you call it? Another signature is a function that takes no inputs, but it can return a value (like readLine() from nodejs), where did it get the value from? Just short of returning a constant value, it had to get it from somewhere.

Building an Application

Building an application requires both pure and impure functions, but how do we leverage the best of both worlds?

When I think about software, I think about how data flows through the system. For example, if someone is using a console application, they're inputting their commands to the terminal, which in turn converts them to commands to run, where the output is displayed on the screen.

As such, an application is made of three kinds of functions.

  • Boundary functions - These are responsible for getting input/output. They should have zero business rules (or the least possible as they are impure functions.
  • Business functions - These are the business specific rules that need to be ran on the given inputs. As these are typically the most important of an application, they are designed as pure functions
  • Workflow functions - This is the combination of boundary components and business components to build something useful. Since they're using impure functions, this will also be impure, but I often use this as my composition root for the application.

Effervescent Applications with Fizz Buzz

To demonstrate, let's build a version of FizzBuzz that uses this mindset.

For the problem, we have the following requirements.

  • If the number is divisible by 3, print "Fizz".
  • If the number is divisible by 5, print "Buzz".
  • If the number is divisible by both 3 and 5, print "FizzBuzz".
  • If the number isn't divisible by any of these, then print the number.

Given that we're building a console application, we will need to support getting input via the console and printing to the console.

Let's go ahead and build up our boundary functions.

// Impure function that allows us to get number from user
function getInput(): number {
  // using prompt-sync
  const prompt = require("prompt-sync")({ sigint: true });
  const response = prompt("What number to calculate FizzBuzz to?");
  if (!+response || +response < 1) {
      "Invalid response, please enter a positive number greater than 1"
    return getInput();
  return +response;

// Function that wraps console.log for printing
function printOutput(content: string): void {

At this point, we have a way of getting a number via getInput and a way to print a string via printOutput. In printOutput, this is a tiny function with no business rules whatsoever. getInput, however, has some business rules about validation, but we'll see later on how to refactor this.

For now, let's leave these two and look into creating our business rule functions.

// Business rules for FizzBuzz
function calculateFizzBuzz(input: number): string {
  if (input % 3 == 0 && input % 5 == 0) {
    return "FizzBuzz";
  if (input % 3 == 0) {
    return "Fizz";
  if (input % 5 == 0) {
    return "Buzz";
  return `${input}`;

// Helper function to create a range of numbers from [1..end]
function createRangeFromOneTo(end: number): number[] {
  if (number < 1) {
    return [];
  return Array.from(Array[number].keys()).map((x) => x + 1);

With calculateFizzBuzz defined, we could write unit tests to ensure the correctness of the behavior. We could also create a mapping to double-check that we have a function.

Now, let's revisit our getInput function. We've got some business rules that deal with validation (e.g. the input must be a number and greater than 1). Given that this is a light business rule, we could leave it here; however, testing this becomes harder because we don't have a way to ensure that the validation works as expected.

To solve this problem, we could extract the validation logic to its own pure function and update getInput to use the new function.

function isInputValid(input: string): boolean {
  if (!+input) {
    return false;
  return +input > 1;

function getInput(): number {
  // using prompt-sync
  const prompt = require("prompt-sync")({ sigint: true });
  const response = prompt("What number to calculate FizzBuzz to?");
  if (!isInputValid(response)) {
      "Invalid response, please enter a positive number greater than 1"
    return getInput();
  return +response;

Nice! With this in place, we can go ahead and implement our last function, the FizzBuzz workflow.

function runFizzBuzzWorkflow(): void {
  // Data coming in
  const maximumNumber = getInput();

  // Calculating results
  const results = createRangeFromOneTo(maximumNumber).map((x) =>

  // Print Results
  results.forEach((x) => printOutput(x));

// example invocation

This is a straightforward implementation as we get the maximumNumber to calculate, create an array of numbers from 1 to maximumNumber, map each of those to their FizzBuzz representation, and then print them to the screen.

Let's go one step forward. In our example, we assumed that the input and output was coming from the console, but what if we needed to change to read and write to a file?

We could move the boundary functions to be parameters to runFizzBuzzWorkflow, let's take a look at what that would give us.

function runFizzBuzzWorkflow(
  readInput: () => number,
  writeOutput: (string) => void
) {
  // Data coming in
  const maximumNumber = readInput();

  // Calculating results
  const results = createRangeFromOneTo(maximumNumber).map((x) =>

  // Print Results
  results.forEach((x) => writeOutput(x));

// example invocations
runFizzBuzzWorkflow(getInput, printOutput); // using console read/write
runFizzBuzzWorkflow(() => 42, printOutput); // using hardcoded input with console log

With this change, we can now swap out how we can input or output by creating new functions with the right type signatures. This makes testing workflow components easy because you can stub in your own mocks (no need for mocking frameworks).

If you understand the power of switching out your boundaries, then you also understand other modern architectures like Ports and Adapters as they follow a similar principle.

Wrapping Up

In this post, we looked at what a function is, how it relates to types, and how to tell if a mapping is a function. From there, we covered the differences between pure and impure functions and how you need both to build any useful application. Finally, we wrapped up by implementing the FizzBuzz problem using this approach.

Five Tips to Improve Your Coaching Conversations

As a leader, you're responsible for coaching and growing your team, helping them be successful. To do this, you need to set the tone and example of the behaviors you want the team to have.

No matter how good of a team you have or how good of a leader you are, you will have to have a conversation about performance. Whether it's delivery, professional skills, or technology skills, you will have a moment where you need someone to change their behaviors.

Having these types of conversations can be scary, no matter how much experience in leadership you might have. However, when done correctly, these moments can greatly impact the other person, helping them grow tremendously.

On the other hand, poor coaching will do the absolute opposite. The other person can become confused or angry. They could even shut down and disengage altogether, making coaching them that much harder.

So what does good coaching look like? I can't guarantee that these steps will solve all your woes; however, I do guarantee that following these tips will increase the odds of the other person listening and at least consider your feedback. Remember, you want to do this coaching because some behavior has caught your attention, and you want to correct it. If the other person doesn't listen or want to engage, then you literally can't make this happen.

Step 1: Be Timely

The sooner you can have this conversation, the more effective it will be. Remember, the point of feedback is to let the other person know how they're doing and correct if needed. They can't do this if the behavior happened three weeks ago because there's no correlation at that point.

Imagine if you had a test suite that only told you about failing tests a week after the build started. There's no way you could make the right decisions, so why would we think that's the case for behavior?

If I've noticed a pattern and feel that it's time to coach, I will get that feedback to them that week, if not the next day.

Step 2: Be Specific

When giving this feedback, the behavior may be obvious to you but not even a thought for the other person. Because we can't control what the other person is thinking, we need to set the context for the feedback so they know what you're talking about.

Let's take my son, for example. He's particular about his food, so when he says that "dinner was awesome," that makes me feel great as I'm happy he enjoyed dinner. But I have no clue what he actually liked or why he thought that. Was it the food? The way it was served? The fact that we had a picnic? No idea, so I'd respond with, "What made it stand out to you?". When he mentions that he liked the pizza, I go "Ah! He enjoyed the food, nice!"

Providing this specific context is crucial for the other person because it lets them kow what caught your attention and drastically reduces the confusion in the conversation. For those who like more concrete details, sharing links to chats, emails, or other artifacts with the behavior can be helpful because you can use it as the foundation for the conversation.

Step 3: Explain Why

There's a reason that you're having this conversation. There's something that's important to you, and, in your opinion, it wasn't important to the other person. We've got to explain why it's important and why you're commenting on it.

I never want to remove someone's autonomy as I like to set the direction and let the team blaze a path, with me guiding to make sure we don't get lost in the wilderness. However, for someone to have autonomy, they need to understand the goals and the reasoning behind it.

If they don't have this knowledge, then it's that much harder for them to make the right decisions. Ensuring they know the why is a leader's responsibility.

Step 4: Seek To Understand

You're working with a team of professionals. A professional makes the right decisions based on their knowledge and experience. If the person is making mistakes, we need to understand why they made the choice that they did.

For example, let's say I'm coaching someone who's consistently missing meetings. I'm frustrated that they're unresponsive and that they don't care. The issue here is that it's okay for me to feel frustrated, but I can't make the judgment that they don't care. I don't know that, and it causes more problems than it solves. I won't vent my feelings to the other person because even though it'd make me feel better, it doesn't help the situation.

A better approach would be to understand why they're missing meetings. Is it something outside of work? Could it be that they don't know why they need to attend? What if they didn't receive an invite? In any of the above cases, there was a solid reason why they didn't attend, and I wouldn't have known that if I had not opened the conversation.

Don't assume malice or apathy when something happens. We are humans first, which means we're going to make mistakes.

Step 5: Working Together

The entire point of coaching is to help the person improve, and we also don't want to take away their autonomy. To make this happen, we need to work with the other person to come up with ideas that can help improve the situation. It's not any one person's responsibility, but it's your responsibility to brainstorm with them and help guide them down the correct path.

The key here is to have an open mind and really consider all ideas. One of my favorite leadership books, First, Break All The Rules, talks about how great leaders work with their people to have their strengths shine and to make their weaknesses a non-issue.

In the missing meeting example, I found out that the issue was that they didn't know why they needed to attend the meeting, so they didn't attend, in order to focus on their development work. Working together, I changed invites to include the reason for attending and encouraged them to chat with me so we could figure it out if they didn't know why they needed to be there.

Case Study - Bringing It Together

In this example, let's explore where we would need to do some coaching.

While reviewing a pull request from Bruce, you see a comment from Alvin, a member of your team, where they were particularly critical of the work. Reading through the pull request, you see Alvin has left more harsh comments about Bruce's work.

Talking with Bruce, they mention that they don't work well with Alvin as it seems like he's always critical of Bruce.

Based on this scenario, we know that Alvin has left some harsh words for Bruce, which makes them less likely to work together. If Alvin keeps this behavior up with other people, this will impact others wanting to work with him, reducing his effectiveness.

After collecting your thoughts, you reach out to Alvin to see if he's got a few minutes to chat about Bruce's pull request.

"Hey Alvin, I noticed you left some pretty harsh comments that in Bruce's pull request. For example, saying that 'this code is convoluted, rewrite it'. Even if that was the case, it's not clear why you think that. I'm more concerned with how the messaging came across because we work with others to accomplish our tasks, and that communication style can make people not want to work with us.

I don't believe you intend to alienate others, so can you walk me through your thought process here and why you thought this was the right approach?"

In this example, we've already hit four out of the five tips. Our feedback was timely and specific to the problem. We included why it caught our attention and started with an open-ended question for the conversation about the behavior.

In the follow-up conversation, Alvin mentions that he was having a rough day, particularly outside of work, and that he wasn't entirely focused on his tone. Given that this is the first time Alvin has done this, we want to focus on fixing the issue before it becomes a pattern.

"I understand that it can be hard to focus on your tone when you're having a rough time, however, we can't speak to others this way. I don't want this to become a pattern, so what are some things that we could do instead when we're not in the right mental head space for code reviews?"

At this point, we've acknowledged what was said and reaffirmed expectations. Using another open-ended question, we can start brainstorming things that we could do to help improve Alvin's tone. Since we're opening the conversation, Alvin is also giving feedback on what might work for him and what wouldn't work.

Wrapping Up

Giving critical feedback to someone is not the easiest thing to do, however, it can have the most impact for them. To help frame the conversation, our coaching should:

  • Be Timely
  • Be Specific
  • Explain the Why
  • Seeking to Understand
  • Be Collaborative

Building Relationships Through One-on-Ones

As a leader, one of your goals is to build a strong, high-performing team. To do this, you'll need to establish and develop relationships within the team and with each other. One approach I've found helpful to build and sustain these relations is through one-on-ones.

When most people think of one-on-ones, they typically think of some scheduled time, every so often, where they talk about work concerns or whatever is on the leader's mind. Some might find one-on-ones a waste of time and skip them.

Let's face it, we've all had bad one-on-ones where the conversation was forced and stiff. Or, it felt like the other person wasn't listening or cared about what was being talked about. If enough one-on-ones go down this route, it's no surprise that people don't want to have these conversations.

So, how do we improve the situation? In this post, I'm going to show you three things you can do to improve the one-on-ones you're having with the team by making sure that they're being heard, relationships are being built, and, just maybe, you might even get to know them better.

It's Not a Status Update

A common mistake is treating one-on-ones as status updates for work or projects. Even though it might be tempting to get an update (especially on important projects), remember this time is for the other person to talk with you about what's on their mind. They can't do this if you're asking for updates on work. If you're leveraging stand-ups or a task board, then you should be able to get updates from there. If this isn't sufficient, ask for updates outside this conversation. The one-on-one is where you give the other person your full attention.

Despite your best intent, this can be a tough habit to break. To help get out of this mindset, start time-boxing the updates to be a set period of time (e.g., ten minutes) with the goal of making this period shorter in subsequent one-on-ones.

Another technique I use is resetting, where I remind my teammate of the purpose and goal of the conversation. Doing this, it's a gentle nudge in the correct direction and reinforces that this time is for them, not for whatever is on my mind.

Don't Get Distracted

In the world of working remotely, it's easy to get distracted by chat notifications or emails. You're on the call, and you see the notification at the bottom of your screen, and before you realize it, you've read it and already thinking about a response. This may be great for you getting things done; however, for the other person, it's clear that you stopped paying attention. So what's important? Is it the notification or the other person?

pedestrians looking distracted in downtown
Credit to Matt Quinn via Unsplash

To help reinforce the focus, I put myself in Do Not Disturb mode, which will hide notifications from me until the meeting ends. If the issue is truly important, then someone would give me a call, in which case, I can excuse myself from the one-on-one to see what's up. In this rare case, I will reschedule our conversation as it's essential that we meet.

Allow Them to Set the Agenda

Another mistake I see leaders make is that they'll come to the one-on-one with a list of topics they want to discuss for the day. This can be particularly true if you're coaching this person and you want to provide concrete feedback. However, remember, the goal is to build and strengthen the relationship, and you can't do that if you're always setting the agenda for the conversations.

I find it amazing that you can learn quite a bit about the other person based on what they bring up. For example, if they're speaking about a conflict with another person, that lets me know that they're aware of relationships and how they're being perceived. On the other hand, if they're talking about a project and the concerns they have, then they're thinking outside of a task and are thinking at a higher level.

In one case, I was in a one-on-one with an engineer where they brought up their concern about supporting an API as they didn't know much about it. My first impression was that they didn't know how to read the code, but digging in, it turned out that they didn't see how the API fit into the bigger picture of the system. Learning this was a great fact check because I thought it was a technical issue, but in reality, it was a system question, which changed my perspective on them.

(Bonus) - Seeding a Conversation

I mentioned that the other person should own the agenda, but sometimes, they may not have much on their mind or a topic that sticks out to them. For these cases, I come prepared with a list of questions to help start the conversation.

pedestrians looking distracted in downtown
Credit to Markus Spiske via Unsplash

In Warren Berger's The Book of Beautiful Questions, he talks about the power of open-ended questions and how they can help people be more open. So instead of asking, "How's the project coming along?", which can be answered in a binary fashion, we could instead ask, "What's one thing about the project that stands out to you?", which could give us a richer response and allow you to learn more.

For those looking for questions, here's an excerpt of questions I've used to help seed a conversation:

  • What's one thing about the current project that turned out to be harder than you thought?
  • What was your biggest win last week, and why does it stand out?
  • What's something that happened in the past week that you want to learn more about?
  • I know you've been working more with this past week, talk to me about that experience
  • What's something that you're looking forward to?

Wrapping Up

To build great teams, you will need to foster relationships with the team and the individual members. Having one-on-ones can help with build these relationships, but only if you treat them like so. By allowing your teammate to set the agenda, giving them your full attention, and cutting out project updates, you can improve the quality of your conversations and get to know them better.

Building Relationships with Intent

As a leader, one of your superpowers is how you can connect your team with someone else. For example, if your team is struggling to work with an API and you know someone who's made recent changes or is a Subject Matter Expert, you can get your team unblocked and moving faster.

I've worked with leaders like this, and it's amazing how fast and helpful it is to get unstuck quickly. Don't get me wrong, sometimes it's the right strategy to "burn the time" to learn, but it's helpful to know someone who can get you unstuck if you need it.

With one leader, it seemed like they always knew a guy, no matter the topic, and I was amazed at how they did it. So like a lifelong learner, I asked, and they told me networking.

large group of people networking
Credit to ProductSchool via Unsplash


If you're like me, you hear networking and think about dozens (if not hundreds) of people milling around, introducing themselves, and sharing business cards. Don't get me wrong, that approach can work for some people, but to me, that sounds exhausting. Instead of a hummingbird, going from flower to flower, I'm more like a bear. I just want to sit down and eat my jar of honey.

So what am I supposed to do? How am I supposed to network if I don't like large groups?

Given time, you can work on becoming more comfortable in large groups. However, why fight your natural tendencies and what you're good at?

For me, it's small groups and one-on-one conversations. As such, that's my approach to networking. Though it takes a bit longer, I find that I build stronger relationships with those people, and in turn, can be just as successful. I like to think about one-on-ones as lazy river conversations as I never know where it will take us.

man sitting in inner tube
Credit to Kiara Kulikova via Unsplash

One Cup of Coffee

At a previous company, we used Slack and, as such, had an integration called Random Coffee that would pair the members of a channel up to get together for the week. Such a simple idea, but so powerful when you now have a built-in excuse to chat with someone.

Coffee Chat
Credit to Priscilla Du Preez via Unsplash

After a couple of weeks of getting to know people, I started learning what others did, what interests them, and who to go to about specific issues. Combine that with asking, "How did you know that?" I found that I could quickly fill gaps in my knowledge.

But something else happened. Once I knew the person, I didn't see them as a name in the chat anymore, I saw them as their selves. I'd find myself saying, "Oh, it's Chris, and Chris is cool, so I'll help him out," instead of thinking, "Ugh, another thing to do." In a way, these conversations humanized those I worked with, and I found myself caring more about them.

Caring By Knowing

To me, this is the most important thing about relationship building and networking. Deep down, I want to care about those I work with because I want them to be successful. I can't help them be successful if I don't know them both as a colleague and as a person.

Having one-on-ones is how I know my people and how I continue building care. It might be as simple as knowing what types of things they like to work on or what they did over the weekend. However, having these conversations helps both of us open up, and I get to know them so much better. Once I know them, I can guide and direct them better, looking for opportunities I wouldn't have thought of before.

How Do I Start?

If you want to start this for your own company, you don't have to have Slack to make this happen. The important thing is getting buy-in from others and explaining the why behind the exercise.

Once you have buy-in, you can start low-tech by using an Excel sheet and randomizing the list of names. This isn't the most robust solution, but it's a start and you can iterate as you figure out the timing, the frequency, and the other steps that setting this up would look like.

Once you've got something in motion, you can always work on automating the process later. Don't let a perfect solution stop you from starting with a good solution.

What I've found successful is having either a weekly or fortnightly scheduled message in our main channel that assigns the groups. From there, participants are encouraged to share something they've learned about their counterparts during their conversation. To help make sure that people meet, scheduling a set time during the week for all the groups can be helpful as it removes another barrier (e.g., if you know that you'll have coffee at 10:30 am on Tuesdays, you learn to expect it).

If you have a group that is just starting, it might be helpful to provide some starting questions to help jump-start the conversation. A good list of questions can be found in one of my gists.

Wrapping Up

To be a successful leader, you must cultivate and grow relationships with those you work with. Not only does it help your team be successful, but it allows you to have a richer experience with your work and helps solidify that we're all working together.

Better Domain Modeling with Discriminated Unions

When I think about software, I like designing software so that doing the right things are easy and doing the wrong things are impossible (or at least very hard). This approach is typically called falling into the pit of success.

Having a well-defined domain model can prevent many mistakes from happening just because the code literally won't let it happen (either through a compilation error or other mechanisms).

I'm a proponent of functional programming as it allows us to model software in a better way that can reduce the number of errors we make.

Let's at one of my favorite techniques discriminated unions.


In the GitHub API, there's an endpoint that allows you to get the events that have occurred for a pull request.

Let's take a look at the example response in the docs.

    "id": 6430295168,
    "url": "",
    "event": "locked",
    "commit_id": null,
    "commit_url": null,
    "created_at": "2022-04-13T20:49:13Z",
    "lock_reason": null
    "id": 6430296748,
    "url": "",
    "event": "labeled",
    "commit_id": null,
    "commit_url": null,
    "created_at": "2022-04-13T20:49:34Z",
    "label": {
      "name": "beta",
      "color": "99dd88"
    "id": 6635165802,
    "url": "",
    "event": "renamed",
    "commit_id": null,
    "commit_url": null,
    "created_at": "2022-05-18T19:29:01Z",
    "rename": {
      "from": "Secret scanning: dry-runs for enterprise-level custom patterns (cloud)",
      "to": "Secret scanning: dry-runs for enterprise-level custom patterns"

Based on the name of the docs, it seems like we'd expect to get back an array of events, let's call this TimelineEvent[].

Let's go ahead and define the TimelineEvent type. One approach is to start copying the fields from the events in the array. By doing this, we would get the following.

type TimelineEvent = {
  id: number;
  url: string;
  event: string;
  commit_id?: string;
  commit_url?: string;
  created_at: string;
  lock_reason?: string;
  label?: {
    name: string;
    color: string;
  rename?: {
    from: string;
    to: string;

The Problem

This definition will work, as it will cover all the data. However, the problem with this approach is that lock_reason, label, and rename had to be defined as nullable as they can sometimes be specified, but not always (for example, the lock_reason isn't specified for a label event).

Let's say that we wanted to write a function that printed data about TimelineEvent, we would have to write something like the following:

function printData(event: TimelineEvent) {
  if (event.event === "labeled") {
    console.log(event.label!.name); // note the ! here, to tell TypeScript that I know it'll have a value
  } else if (event.event == "locked") {
  } else {
    console.log(event.rename!.from); // note the ! here, to tell Typescript that I know it'll have a value

The main problem is that the we have to remember that the labeled event has a label property, but not the locked property. It might not be a big deal right now, but given that the GitHub API has over 40 event types, the odds of forgetting which properties belong where can be challenging.

The pattern here is that we have a type TimelineEvent that can have different, separate shapes, and we need a type that can represent all the shapes.

The Solution

One of the cool things about Typescript is that there is a union operator (|), that allows you to define a type as one of the other types.

Let's refactor our TimelineEvent model to use the union operator.

First, we need to define the different events as their own types

type LockedEvent = {
  id: number;
  url: string;
  event: "locked"; // note the hardcoded value for event
  commit_id?: string;
  commit_url?: string;
  created_at: string;
  lock_reason?: string;

type LabeledEvent = {
  id: number;
  url: string;
  event: "labeled"; // note the hardcoded value for event
  commit_id?: string;
  commit_url: string;
  created_at: string;
  label: {
    name: string;
    color: string;

type RenamedEvent = {
  id: number;
  url: string;
  event: "renamed"; // note the hardcoded value for event
  commit_id?: string;
  commit_url?: string;
  created_at: string;
  rename: {
    from: string;
    to: string;

At this point, we have three types, one for each specific event. A LockedEvent has no knowledge of a label property and a RenamedEvent has no knowledge of a lock_reason property.

Next, we can update our definition of TimelineEvent to use the union operator as so.

type TimelineEvent = LockedEvent | LabeledEvent | RenamedEvent;

This would be read as A TimelineEvent can either be a LockedEvent or a LabeledEvent or a RenamedEvent.

With this new definition, let's rewrite the printData function.

function printData(event: TimelineEvent) {
  if (event.event == "labeled") {
    console.log(; // note that we no longer need !
  } else if (event.event == "locked") {
  } else {
    console.log(; // note that we no longer need !

Not only do we not have to use the ! operator to ignore type safety, but we also have better autocomplete (note that locked_reason and rename don't appear when working with a labeled event). Better autocomplete

Deeper Dive

At a general level, what we've modeled is a sum type and it's great for when you have a type that can take on a finite number of differing shapes.

Sum types are implemented as either tagged unions or untagged unions. Typescript has untagged unions, however, other languages like Haskell and F#, use tagged unions. Let's see what the same implementation in F# would have looked like.

// specific type definitions omitted since they're
// similar to typescript definition
// ....
type TimelineEvent = Locked of LockedEvent | Labeled of LabeledEvent | Renamed of RenamedEvent

let printData e =
    match e with
    | Locked l -> printf "%s" l.lock_reason
    | Labeled l -> printf "%s"
    | Renamed r -> printf "%s" r.rename.``to`` // the `` is needed here as to is a reserved word in F#

A tagged union is when each shape has a specific constructor. So in the F# version, the Locked is the tag for the LockedEvent, Labeled is the tag for the LabeledEvent, so on and so forth. In the Typescript example, we worked around it because the event property is on every TimelineEvent and is a different value.

If that wasn't true, then we would had to have added a field to TimelineEvent (typically called kind or tag) that would help us differentiate between the various shapes.

Wrapping Up

When defining domain models where the model can have different shapes, you can use a sum type to define the model.

Keeping Track - My Task Tracking Approach

When it comes to keeping track of things to do, I recall an ill-fated attempt at using a planner. My middle school introduced these planners for the students that you had to use to keep track of dates (and, weirdly enough, as a hall pass to go to the bathroom).

Looking back, the intent was to have the students be more organized, but that wasn't what I learned. I found it cumbersome and a pain to keep track of. Also, you had to pay to replace it if it was lost or stolen.

What I learned to do instead was to keep track of everything I needed to do in my memory, and if I forgot, well, I had to pay the penalty.

I recall seeing my peers in high school and college be much more organized, and they made it so simple. Just color code these things, add these other things to a book and highlight these things.

I didn't realize that my peers had developed a system for studying and keeping track of what they needed to do. Since I didn't know what it was called and felt awkward admitting I didn't know what it was, I would continue relying on my memory to get things done. However, this approach doesn't scale and is prone to having tasks drop from the list.

When I started working at my second professional job, I found my boss to be organized and meticulous, and he never let anything slip. I learned a ton from him about process improvement and was introduced to a Kanban board for the first time.

As an engineer, I would use a version of his approach for years, but when I got into leadership, I felt that I needed a better system. As an individual contributor, I could rely on the task board for what I needed to do, but that approach doesn't work for a leader because not all of your tasks are timely or fit in a neat Jira ticket.

Why a System?

Why do we need a system at all? Isn't memory good enough? The problem is that the human mind is fantastic at problem-solving but isn't great when it comes to recollection. In fact, multiple studies (like this one or this one) have shown that the more stressed you are, the worse your memory can become.

With this context, you need to have some system to get the tasks out of your head and stored elsewhere. Whether that's physical sticky notes in your office, a notebook that you use, or some other tooling, I don't particularly care, but you do need something.

My Approach

I'm loosely inspired by the Getting Things Done approach to task completion, which I've implemented as a Trello board. Having an online tool works for me because I can access it anywhere on my phone (no need to carry a notebook or other materials).

Another side effect of having an online tool is that at any point I have an idea or a task that I need to do, I can add it to my Trello board in two clicks. No more worries about remembering to add the task when I'm back home or in the office, which allows me to not stress about it.

Work Intake Process

On my Trello board (which you can copy a template from here), all tasks end up in the first column, called Inbox. The inbox is the landing spot for anything and everything. Throughout the day, I will process the list and move it to the appropriate column.

  • Is it a task that I can knock out in 5 minutes or less? Just do it!
  • Is it a task that will take more than 5 minutes? Then I move it into the To Do column
  • Is it a task that I might be interested in? Is it a bigger task that I need to think more about? Then that goes into the Some Day column
  • If the task is no longer needed, then it gets deleted.

Deciding What To Do Next

Once the inbox is emptied, I look at the items in the To Do column and pick the most important one. However, determining the most important one is not always the easy.

For this, I leverage the Eisenhower Matrix approach.

Named after Dwight D. Eisenhower, the idea is that we have two axes, one labeled Important and the other labeled Urgent. With these labels, tasks fall into four buckets:

  • Urgent and Important - (e.g., production broken, everything is on fire)
  • Urgent and Not Important - (e.g., last minute request, something that needs to be done, but not necessarily by you)
  • Not Urgent and Important - (e.g., strategic work, things that need to get done, but not necessarily this moment)
  • Not Urgent and Not Important - (e.g., time wasters, delete these tasks)
Eisenhower Matrix with four quadrants: Urgent & Important, Urgent & Not Important, Not Urgent & Important, and Not Urgent & Not Important
(2023, March 7). In Wikipedia.

Dealing with Roadblocks

In an ideal world, you could take an item and run it to completion, but things aren't always that easy. You might need help from another person or are waiting for someone to do their part.

When this happens, I'll move the item to the Waiting column and pick up a new task as I don't like to be stalled.

However, I keep an eye on the number of items in flight as I've found that if I have more than three items in flight, I struggle with making progress and spend my time context-switching between the items instead of completing work. It can be challenging if the tasks are wholly unrelated (development tasks, writing, and reviewing pull requests) as the cost of regaining the context feels higher than if the tasks are related (e.g., reviewing multiple pull requests for the same repository).

Getting Things Done

As items get completed, I add them to the Done column for the week. To help keep track of what I got done for the week, I typically call my Done column the week it spans (e.g., Apr 17-23, 2023). Once the week ends, I can refer back to the column, see where I spent my time, and reflect if I made the right choices for the week.

Finally, I'll archive the list, create a new column for next week and repeat.

Telling the Story: The Pitfall of a Single Data Point

Let's say that you're sitting down to read a new book, and you come across the following:

The King's Knave Inn was but a short distance from the Alverston train depot, just outside the town proper. (excerpt from The Infernal Machine by John Lutz)

After reading this, a friend interrupts your reading and asks your thoughts on the book so far. What would you say?

Most likely, you'd respond that you need to read more, and it's still too early to decide if the book is good or not.

To honestly answer this question, you would need to read more of the book (ideally all of it) to get a full picture of the story.

When measuring an engineer's performance and effectiveness, why don't we take the same approach?

My experience has been that leaders look for one or more metrics to quantify a person. At the face of it, I understand why, as it's hard to compare people if there aren't numbers.

However, the mistake I see leaders make is what they're trying to measure. For example, do you measure the number of pull requests? What about the number of stories completed in a sprint? How about the number of bugs shipped to production? Something else entirely?

The problem is that even if you use all of the above (please don't do this), you're still not seeing the whole picture, but only bits and pieces. This would be like reading five chapters at random from a book and then giving an opinion.

The other problem with using metrics is that the measurement will cease to be effective as people will start gaming the system (see Goodhart's Law).

For example, if we measure effectiveness by the number of completed pull requests, then what stops someone from creating hundreds of single-line pull requests that don't accomplish anything?

On the other side, what about the engineer who reduced scope and time because they knew how to simplify the approach or came up with a more straightforward solution? This insight won't show up as a pull request or a completed story; however, this should be rewarded just the same.

To really determine how effective someone is, we need to look at things holistically, which can be done by examining how well someone does in these three areas:

  • Understanding the problem (e.g., why are we doing this?)
  • Understanding the system (e.g., how are we doing this?)
  • Understanding the people (e.g., whom are we doing this with?)

By looking into these areas, you will see what your team is good at and where they could use coaching, helping you be more effective. You might also realize that your team is doing things that aren't so obvious.

You can't write a report to generate these metrics. To understand this, you have to understand your team and how they work together. This involves paying attention, taking notes, and being engaged. Passive leaders will struggle if they use this approach.

Understanding the Problem (The Why)

To be successful, we first have to understand the problem that's being solved. Without this base knowledge, it's impossible to build the right solution or even ask the right question to the problem at hand.

How comfortable are they within the problem domain? Do they know certain terminologies, our customers, the users, workflows, and expected behaviors?

Besides quizzing, there may not be an obvious way to measure this; however, here's my approach.

First, you can look at the questions that are being asked. Are they surface level or are they deep? You can see these questions through chats and meetings, comments on the stories or pull requests, and interactions with others.

Second, look at the solution they came up with. Did they design it with domain knowledge in mind? For example, are things named correctly? Did their solution take care of the main workflows? What about the edge cases?

Third, how are they handling support issues? Being on support is a quick way of learning a problem domain and system. As such, I'm looking at how much help they need and how they communicate with others.

By using this approach, you can get a good sense of how knowledgeable someone is in the problem domain without quizzing them.

Understanding the System (The How)

There's always a push to deliver more things, and in order to do that, we have to understand the current system, its limitations, what's easy vs. what's hard, and from these constraints, determine the correct path to take.

In addition, once the system is live, we need to support it. If we don't know the moving parts, what it interacts with, and how it's used, we're going to have a bad time.

Like understanding the problem, we can measure system knowledge without quizzing them. In particular, I've found pull request comments and code reviews to be insightful on someone's knowledge of the system.

For example, do they call out that there's already something in the system that does this new piece of functionality? Do they suggest taking a simpler approach with what we have? Do they propose a different solution altogether because the system has a limitation? All of these are indicators of someone's system knowledge.

Another way to gauge system knowledge is by looking at how the person handles support requests. If you can understand the problem, find the cause, and create a fix, then by definition, you have to have a solid understanding of the system.

Understanding the People (The Who)

When it comes to the third part of being effective, we have to measure how they work with those around them. Most people think engineering is a solitary line of work, and that can be true when it comes to the development phase.

However, in reality, engineers work with others to design, develop, and iterate on a solution, and this can only happen when working with others. As such, building these relationships are paramount to being successful.

If you want to go fast, go alone. If you want to go far, go together.

Measuring team cohesion can be difficult (it could be its own post), however, we start simply be getting peer feedback on the person. We can also look at the communication between them and others through their comments, messages, or meetings.

Another way to measure this is through your company's recognition system. Whether it's an email or some other tool your company uses, you need to keep tabs on these recognitions, as you can use them as a talking point during 1:1s and review time.

Wrapping Up

So, how do we measure how effective someone is? We know that a single data point isn't sufficient and that if we limit ourselves to metrics, we can get a skewed sense of the person. To know, we have to take a holistic approach.

To accomplish this goal, I recommend measuring the following areas:

  • Understanding the problem (e.g., why are we doing this?)
  • Understanding the system (e.g., how are we doing this?)
  • Understanding the people (e.g., whom are we doing this with?)

In each of these areas, we can get a sense by observing their interactions they have, the questions they ask, the approaches they take, and how likely people want to work with the individual.