Hi, I’m Redowan

One neat use case for the HTTP ETag header is client-side HTTP caching for GET requests. Along with the ETag header, the caching workflow requires you to fiddle with other conditional HTTP headers like If-Match or If-None-Match. However, their interaction can feel a bit confusing at times. Every time I need to tackle this, I end up spending some time browsing through the relevant MDN docs123 to jog my memory. At this point, I’ve done it enough times to justify spending the time to write this....

Every once in a while, I find myself skimming through the MDN docs to jog my memory on how CORS1 works and which HTTP headers are associated with it. This is particularly true when a frontend app can’t talk to a backend service I manage due to a CORS error2. MDN’s CORS documentation is excellent but can be a bit verbose for someone just looking for a way to quickly troubleshoot and fix the issue at hand....

Ever since Rob Pike published the text on the functional options pattern1, there’s been no shortage of blogs, talks, or comments on how it improves or obfuscates configuration ergonomics. While the necessity of such a pattern is quite evident in a language that lacks default arguments in functions, more often than not, it needlessly complicates things. The situation gets worse if you have to maintain a public API where multiple configurations are controlled in this manner....

In 9th grade, when I first learned about Lenz’s Law1 in Physics class, I was fascinated by its implications. It states: The direction of an induced current will always oppose the motion causing it. In simpler terms, imagine you have a hoop and a magnet. If you move the magnet close to the hoop, the hoop generates a magnetic field that pushes the magnet away. Conversely, if you pull the magnet away, the hoop creates a magnetic field that pulls it back....

These days, I don’t build hierarchical types through inheritance even when writing languages that support it. Type composition has replaced almost all of my use cases where I would’ve reached for inheritance before. I’ve written1 about how to escape the template pattern2 hellscape and replace that with strategy pattern3 in Python before. While by default, Go saves you from shooting yourself in the foot by disallowing inheritance, it wasn’t obvious to me how I could apply the strategy pattern to make things more composable and testable....

While I like Go’s approach of treating errors as values as much as the next person, it inevitably leads to a situation where there isn’t a one-size-fits-all strategy for error handling like in Python or JavaScript. The usual way of dealing with errors entails returning error values from the bottom of the call chain and then handling them at the top. But it’s not universal since there are cases where you might want to handle errors as early as possible and fail catastrophically....

I used reach for reflection whenever I needed a Retry function in Go. It’s fun to write, but gets messy quite quickly. Here’s a rudimentary Retry function that does the following: It takes in another function that accepts arbitrary arguments. Then tries to execute the wrapped function. If the wrapped function returns an error after execution, Retry attempts to run the underlying function n times with some backoff. The following implementation leverages the reflect module to achieve the above goals....

Despite moonlighting as a gopher for a while, the syntax for type assertion and type switches still trips me up every time I need to go for one of them. So, to avoid digging through the docs or crafting stodgy LLM prompts multiple times, I decided to jot this down in a gobyexample1 style for the next run. Type assertion Type assertion in Go allows you to access an interface variable’s underlying concrete type....

I’ve been a happy user of pydantic1 settings to manage all my app configurations since the 1.0 era. When pydantic 2.0 was released, the settings portion became a separate package called pydantic_settings2. It does two things that I love: it automatically reads the environment variables from the .env file and allows you to declaratively convert the string values to their desired types like integers, booleans, etc. Plus, it lets you override the variables defined in ....

As of now, unlike Python or NodeJS, Go doesn’t allow you to specify your development dependencies separately from those of the application. However, I like to specify the dev dependencies explicitly for better reproducibility. While working on a new CLI tool1 for checking dead URLs in markdown files, I came across this neat convention: you can specify dev dependencies in a tools.go file and then exclude them while building the binary using a build tag....

I love dynamically typed languages as much as the next person. They let us make ergonomic API calls like this: import httpx # Sync call for simplicity r = httpx.get("https://dummyjson.com/products/1").json() print(r["id"], r["title"], r["description"]) or this: fetch("https://dummyjson.com/products/1") .then((res) => res.json()) .then((json) => console.log(json.id, json.type, json.description)); In both cases, running the snippets will return: 1 'iPhone 9' 'An apple mobile which is nothing like apple' Unless you’ve worked with a statically typed language that enforces more constraints, it’s hard to appreciate how incredibly convenient it is to be able to call and use an API endpoint without having to deal with types or knowing anything about its payload structure....

While I tend to avoid *args and **kwargs in my function signatures, it’s not always possible to do so without hurting API ergonomics. Especially when you need to write functions that call other helper functions with the same signature. Typing *args and **kwargs has always been a pain since you couldn’t annotate them precisely before. For example, if all the positional and keyword arguments of a function had the same type, you could do this:...

I needed to integrate rate limiting into a relatively small service that complements a monolith I was working on. My initial thought was to apply it at the application layer, as it seemed to be the simplest route. Plus, I didn’t want to muck around with load balancer configurations, and there’s no shortage of libraries that allow me to do this quickly in the app. However, this turned out to be a bad idea....

You can use @dataclass(frozen=True) to make instances of a data class immutable during runtime. However, there’s a small caveat—instantiating a frozen data class is slightly slower than a non-frozen one. This is because, when you enable frozen=True, Python has to generate __setattr__ and __delattr__ methods during class definition time and invoke them for each instantiation. Below is a quick benchmark comparing the instantiation times of a mutable dataclass and a frozen one (in Python 3....

When I started my career in a tightly-knit team of six engineers at a small e-commerce startup, I was struck by the remarkable efficiency of having a centralized hub for all the documents used for planning. We used a single Trello board with four columns—To-do, Doing, Q/A, Done—where the tickets were grouped by feature tags. We’d leverage a dummy ticket as an epic to sketch out the full plan for a feature and link related tickets to it....

I’ve always had a thing for old-school web tech. By the time I joined the digital fray, CGI scripts were pretty much relics, but the term kept popping up in tech forums and discussions like ghosts from the past. So, I got curious, started reading about them, and wanted to see if I could reason about them from the first principles. Writing one from the ground up with nothing but Go’s standard library seemed like a good idea....

Despite using VSCode as my primary editor, I never really bothered to set up the native debugger to step through application code running inside Docker containers. Configuring the debugger to work with individual files, libraries, or natively running servers is trivial1. So, I use it in those cases and just resort back to my terminal for debugging containerized apps running locally. However, after seeing a colleague’s workflow in a pair-programming session, I wanted to configure the debugger to cover this scenario too....

Data classes are containers for your data—not behavior. The delineation is right there in the name. Yet, I see state-mutating methods getting crammed into data classes and polluting their semantics all the time. While this text will primarily talk about data classes in Python, the message remains valid for any language that supports data classes and allows you to add state-mutating methods to them, e.g., Kotlin, Swift, etc. By state-mutating method, I mean methods that change attribute values during runtime....

Despite being an IC for the bulk of my career, finding my groove amidst the daily torrent of meetings from the early hours has always felt like balancing on a seesaw during a never-ending earthquake. Now, pair that with the onslaught of Slack inquiries and the incessant chiming of email notifications, and you have a front-row ticket to the anxiety circus. There are days when carving out a single hour of focus time is a wild goose chase, pushing me to work after hours to get stuff done, followed by a guilt trip about screen-gazing my life away....

Ever been in a situation where you landed a software engineering job with a particular tech stack, mastered it, switched to another company with a different stack, nailed that too, and then found yourself in a third company that used the original stack? Now, you suddenly sense that your hard-earned acumen in that initial stack has not only atrophied over the years but also a portion, or all of it, has become irrelevant, making it a bit of a struggle to catch up with the latest changes....