Engineering manager and developer
When I joined Cheddar I was pleasantly surprised to find a sharp, mostly minimalist development culture which was a pleasant departure from the ZIRP-era “platform and team sprawl” that was in full bloom at WeTransfer. The mostly-Shopify-inspired mindset - the Shopify of roughly 2012-2014, when Bouke and Tariq were there, long before the sharded-the-world Shopify of today - was extremely poignant…
My good mate Yaroslav wrote about his new solution for bundling a complete Bun runtime inside a gem - by all means, give it a read. A lot of points he makes are very sensible, but for a few months now I have decided that - for myself - I will not be using any frontend bundling nor JS runtime at all. Here’s how you can do the same. How useful is an asset pipeline? There is, in fact, just one…
This is the concluding article in the series On the Way to Step Functions - you will find the other articles linked below: On the way to step functions: Part 1 On the way to step functions: Part 2 On the way to step functions: Part 3 We have established a few important points so far. The spirit, the desiderata of durable execution comes from the desire to have marshalable stacks - which are…
Reading the article about Nexus that Obie has posted I got absolutely struck. Yes, it can be said without a shade of doubt that the modern way of building software, the late-2025-way with Opus 4.5 in the picture, is markedly different from the one we operated in for the last decade (or more). I haven’t been sitting on my hands either. One of my smaller pursuits, now that I am a proud self-employed…
This is the next article in the series On the Way to Step Functions - you will find the other articles linked below: On the way to step functions: Part 1 On the way to step functions: Part 2 On the way to step functions: Part 3 On the way to step functions: Part 4 We have highlighted that DAGs are actually the underpinning of any workflow/durable computation engine (barring serializable…
This is the next article in the series On the Way to Step Functions — you can find the first article in the series here. Previously, I have outlined the ambient desire in the field (marshalable stacks) and described why that is largely unachievable. But if imperative invocations can’t bid us consolation, what could? DAGs, in fact. If you are impatient (and a Rails user) - just head to the…
Lately, it has been a great challenge to get into the world of durable execution. Granted, in the world of web applications we often do not need it. However, anyone who has come in contact with electronic payments, money orders, verifications - will likely encounter a need for durable execution. The juggernauts in the space are, of course, Temporal.io - with the recently emerging contender restate…
The new LLM world is very exciting, and I try to experiment with the new tools when I can. This includes building agentic applications, one of which is my personal accounting and invoicing tool - that I wrote about previously As part of that effort I started experimenting with RubyLLM to have some view into items in my system. And while I have used a neat pattern for referencing objects in the…
Two remarkable posts on HN today: the new release of Affinity is now free and Canva-subsidized and Free software scares normal people There is a bit to unpack as to why these two are related: the first is about Affinity, which is a remarkable and very feature-complete suite of applications for graphics, and the other is about Handbrake having an “intimidating” UI. The two are in perfect…
We get attached to code - sometimes to a fault. Old migrations are exactly that. They’re digital hoarding at its finest, cluttering up your codebase with files that serve absolutely no purpose other than to make you feel like you’re preserving some kind of historical record. But here’s the brutal truth: your old migrations are utterly useless. They’re worse than useless - they’re actively harmful.…
Sometimes, after a few pints in a respectable gathering of Rubyists, someone will ask me “what is the most undervalued module in the Ruby standard library?” There are many possible answers, of course, and some favoritism is to be expected. Piotr Szotkowski, who untimely passed away this summer, did a wonderful talk on the topic a wee while back. My personal answer to that question, however, would…
My previous article about timezones turned out to be useful for quite a few folks, which makes me happy. One candle lights another. Ben Sheldon asked about then actually doing something with those converted times. How do you actually send a newsletter every morning on every working day, regardless of what the user’s time zone is? There are a number of approaches to this - once you know the UTC…
The recent Ruby Central tragedy has me in shambles, honestly. It cuts deep at the very spot where I am feeling the most insecurity and the most disenfranchisement. The crux of the issue is creative control. Writing software is a creative endeavor, and we are just now barely getting to the understanding that even though free software promises open source, it does not promise open governance or…
Doing something at a time convenient for the user is a recurring (sic!) challenge with web applications. And the more users you have across a multitude of time zones, the more pressing it becomes to do it well. It is actually not that hard, but it does have a few fiddly bits which can be challenging to put together. So, let’s do some time traveling.
On the 30th of August, 2000, a train flew out of the tunnel at a station in Paris, and, without stopping, rolled on through into the tunnel. It was clear that the train was speeding, and speeding severely. Inside the tunnel, the train has derailed with the front cab car turning over. Luckily, there were no fatalities. 24 people were injured. The investigation was able to establish that the train’s…
Good ideas are worth disagreeing with. Sean Goedecke posits that organizations implement process to have legibility – a very interesting idea. However, I see it differently. It is not about legibility but it is about perception of legibility. Does the CEO look at burndown charts in your project management tool? Maybe, but highly unlikely. Does the head of product look at the key user flows that…
In the brave new world of self-employment one thing I found very important is getting a grip on time. In general, this turns out to be the biggest challenge for me personally - not having kids and no longer living with a partner I have way more free time than is customary for a 40+ year old, and it shows. And it is becoming more important to get a good understanding of both where the time gets…
Eelco recently wrote about using subdomains in Rails, outlining a seemingly neat idea about having them as subdomains in production but using paths in development. It is clever and looks very usable at first sight. It’s also a very bad idea that is likely to get you side effects you really won’t be happy about. I normally don’t do “rebuttal” posts, but in this case — since I have dealt with that…
A while ago, Simon Willison expressed the idea that SQLite enables a very neat pattern whereby software can carry its datasets in the form of SQLite databases. Such a database is to be used only to read from, and actually presents a very neat, portable, universal data structure for querying a dataset that would otherwise need to be loaded into memory and structured manually. For dynamic and…
Software is a creative endeavor and a craft. And like any creative endeavor and any craft, it is subject to fashions. About a decade ago, one of those fashions was Hexagonal Rails largely inspired by the DDD book, but also by the original Hexagonal Architecture work by Dr. Cockburn. Some of these applications are now up for their Rails upgrade and an “oil change,” and it’s interesting to see them…
A few months ago my partner-in-love-and-in-crime came with a seemingly innocuous request, which went as follows: We have an event coming up, and I need to send out a press release via email. It’s simple enough - just a couple of images and a few blurbs of text. I can’t seem to be able to make it look good in Gmail nor in Apple Mail. How does one do such a thing? Now, we computer-savvy household…
Since 2021 I have been working at Cheddar Payments, which is a fledgling fintech startup in the UK. It was a substantial change from WeTransfer in terms of the problem domain, but also scale. The scale at a B2C fintech is smaller, but the challenges are, in ways, much harder. And the biggest challenge - engineering-wise - is “data over time”. I’ve learned more about data over time than I would…
A while ago, a prominent Vercel employee (two, actually) posted to the tune of: Developers don’t get CDNs Exhibit A etc. It is often that random tweets somehow get me into a frenzy – somebody is wrong on the internet, yet again. But when I gave this a second thought, I figured that… this statement has more merit than I would have wanted it to have. It has merit because we do not know the very…
I’ve needed this before - a couple of times, just like that other thing. A situation where I am doing uploads using AJAX - or performing some other long-running frontend tasks, and I don’t want to overwhelm the system with all of them running at the same time. These tasks may be, in turn, triggering other tasks… you know the drill. And yet again, the published implementations such as p-queue and…
The sites which are using Shardine do not only have separate data storage - they all have their own domain names. I frequently need to validate that every site is able to work correctly with the changes I am making. At Cheddar we are also using multiple domains, which is a good security practice due to CORS and CSP. Until recently I didn’t really have a good setup for developing with multiple…
There is a pattern I am very fond of - “one database per tenant” in web applications with multiple, isolated users. Recently, I needed to fix an application I had for a long time where this database-per-tenant multitenancy utterly broke down, because I was doing connection management wrong. Which begat the question: how do you even approach doing it right? And it turns out I was not alone in this.…
Hot on the heels of the previous article I was asked about my idea of having co-located CSS. Now is the time to share, so read on! Update (2026-02-7) Most of the points in the article still stand, but with @scope now being baseline you can use use it in addition - or instead - of the nested classes.
The day was nearing to a close. The sun has already set, but that Friday evening in Amsterdam was still warm. Unusually warm, in fact, for those late days in March – as if spring decided to bless my pilgrimage, for that pilgrimage was not jovial. I was sitting at a ramen joint, sipping on the broth. To my left, a blue, crinkled supermarket shopping bag was sitting solemnly, inconspicuously. Inside…
I’ve needed this before - a couple of times. Third time I figured I needed something small, nimble - yet complete. And - at the same time - wondering about how to do it in a very simple manner. I think it worked out great, so let’s dig in. Most UIs will have some form of undo functionality. Now, there are generally two forms of it: undo stacks and version histories. A “version history” is what…
Having the same architecture problems over and over does give you perspective. We all love making fun of the enterprise FizzBuzz but there are cases where those Factories, Adapters and Facades are genuinely very useful, and so is dependency injection. Since I had to do dependency injection combined with adapters a wee many times now, it seems like a good idea to share my experience. What I will…
There is a lot of talk that big-tech companies are willing to pay way more, way up north of the market to the local rates. They all seem similar: Pre-IPO or public Looking for senior software engineers or staff engineers Salary brackets never published, and even recruiters stay fairly tight lipped So-described “transparent” interview process - usually a marathon of systems design, “culture fit”…
A while ago I got really triggered by by the following two tweets - one by Avdi and another by Pete This essay was on my mind - and lying dormant - for a couple of years, but I think it didnt lose its relevance.
An interesting twist in my recent usage of SQLite was the fact that I noticed my research scripts and the database intertwine more. SQLite is unique in that it really lives in-process, unlike standalone database servers. There is a feature to that which does not get used very frequently, but can be indispensable in some situations. By the way, the talk about the system that made me me to explore…
In my work I tend to reach for SQLite more and more. The type of work I find it useful for most these days is quickly amalgamating, dissecting, collecting and analyzing large data sets. As I have outlined in my Euruko talk on scheduling, a key element of the project was writing a simulator. That simulator outputs metrics - lots and lots of metrics, which resemble what our APM solution collects.…
Joke Accounts and the BOFH are Garbage by Aurynn Shaw struck a chord with me back in the day. After all, who wants to exclude people? Who wants to make them feel unwelcome? Having survived some amount of difficult working experiences I have changed my mind on this drastically. The joke accounts are a bitter necessity, and I’ll try to explain why.
Well-made software has a lifetime, and the lifetime is finite. However, sometimes software becomes neglected way before its lifetime comes to an end. Not obsoleted, not replaced - just.. neglected. Recently I have decided to resurrect one such piece of software. See, zip_tricks holds a special place in my heart. It was quite difficult to make, tricky, but exceptionally rewarding. It also went…
From my other posts it might seem that I am a bit of a React hater - not at all. React and related frameworks have introduced a very powerful concept into the web development field - the concept of materialised trees. In fact, we have been dealing with those in Rails for years now as well. Standard Rails rendering has been a cornerstone of dozens of applications to date, and continues to be so.…
Feature flags are amazing. No, really, did I tell you that feature flags are amazing? They are. But you might be running a thousand applications. When this kind of complexity gets involved you might need to test combinations of feature flags, sometimes - dozens of those combinations. Exhaustive testing to the rescue!
Marco Rogers started a remarkable thread on Mastodon, which absolutely struck it home for me. Teams absolutely do get mired up in complex tooling. They absolutely can be unprepared, and there absolutely is a skew between the newly-minted “frontend” and “backend” ecosystems. I might have a few things to say about this.
Feature flags are awesome. But just like user preferences or settings they have the tendency of turning your application into multiple applications, all embedded in one.
There is a popular meme that has been going around for years now, This is in fact close to heart for every passionate technologist. Most of use have either been the guy at the desk, or an innocent passer-by willing to enter the conversation. With fairly expected results.
Every succesful application evolves. Business logic is often one of the things that evolves the most, but it is customary to have data which changes over time. Sometimes - over months or years. A lot of spots have logic related to “data over time”. For example: you collect payments from users, but some users were not getting charged VAT. Your new users need to get charged VAT, but they will also…
It is curious how people tend to bash DDD. I must admit - I never worked in a full-on DDD codebase or on a team that practices it, but looking at the mentioned articles like this one does make me shudder a little. There is little worse than a premature abstraction, and a there is a noticeable jump (or rather: a trough) which goes from abstraction to indirection. I’ve been programming for more than…
A list where you can reorder items is one of entrenched widgets in UIs. Everyone knows how they are supposed to work, they are cheap to build, intuitive and handy. The problem is that they often get built wrong (not the “just grab Sortable.js and be done with it”-kind-of-wrong, but the “Sortable.js does not provide good user experience”-kind-of-wrong). I’ve built a couple of these for various…
One of the joys of approaching the same problem multiple times is narrowing down on a number of solutions to specific problems which damn work. One of those are idempotency keys - the other are, undoubtedly, rate limiters based on the leaky bucket algorithm. That one algorithm truly blew my mind the first time Wander implemented it back at WeTransfer. Normally when people start out with rate…
It has recently become a hot topic that junior developers are having difficulties finding a job, even though the market is very hot at the moment. Market for senior talent is, yes, but for juniors - not so much. As a matter of fact it has been flagged that it is harder than ever for a beginner to start a career in software. Multiple causes have been outlined: Companies do not want to invest into…
I’ve already touched on it a bit in the article about doing the scariest thing first – one of the things we managed to do at WeTransfer before I left was implementing proper idempotency keys for our storage management system (called Storm). The resulting gem is called idempo and you use it about like this: config.middleware.insert_after Rack::Head, Idempo, backend:…
In software we pride ourselves in being “data-informed”, “metrics driven”, and “formally proven” is the highest praise. Few things feel as satisfying as being actually right, with no shadow of a doubt and no way of escape for our opponents. Being tech people, we cling to this idea that “the more correct” idea, or the one which is “objectively right”, should win. Now, do not underestimate this: As…
Science establishes concepts that describe nature, and is often able to signal binary answers to questions. “Can acceleration be non-0 when velocity is 0?” “What is the circumference of a circle?” “How many chromosomes does a fruit fly genome contain?” Art, unlike science, speaks to our emotion. Great art is great exactly because - in addition to execution - it stimulates us to imagine something…
I know the pieces fit, cause I watched them fall apart Kir recently wrote about fragmented prototyping which struck a nerve. I use a very similar approach for gnarly engineering and system design problems, so figured I could share while we are at it. I call it the maximum pain upfront approach. Another name could be do the thing that scares you the most first. It goes roughly like this. When you…