Paul Grenyer

Posts

Deep Imports Considered Harmful

Keep It Loose Deep down we all know it’s important to componentise software systems. It allows different parts of the systems, the components, to change and evolve over time with minimal effect on other parts of the system. Designed and implemented correctly, components are loosely coupled , as well as highly cohesive . In practice this means that components can be changed, replaced, or evolved independently, without causing widespread change throughout the system. Components with responsibilities, and that naturally change together, are grouped together. Components have abstract interfaces and concrete implementations. Interfaces describe the features provided by a component and hide the concrete implementation. Users of components - usually other components - depend on the interface rather than the concrete implementation. If clients come to depend on concrete implementations - the internal details of a component - the benefits of componentisation are lost. The comp...

Persepolis Rising

Persepolis Rising is set thirty years later and goes off in a different and uninteresting direction. It is of course possible that the entire book is setting up the story for the final two to be brilliant, but the story arc is only referenced in the epilogue. At the beginning the story makes the reader feel that there is no resisting the invading forces and initial resistance attempts fail and result in surrender. However, by far the best part of the book, other than the epilogue, is when Holden’s team find a way to hijack one of the invader’s ships. There are only two books to go, maybe it will pick up.

Configuring Claude Code to Enforce Your Own Guidelines

I’ve been using Claude Code without many rules for a while. It’s certainly not the most efficient or effective way to use it. With its help, I learnt how to create some persistent rules around logging. When we’d finish I had Claude produce this blog post. It’s been reviewed and revised by me. See what you think. The Problem with Tribal Knowledge Most teams have coding guidelines. They live in many places, including wikis, onboarding documents, and the heads of senior engineers who will politely point out in code review that you shouldn't log the request body. The problem is that guidelines only work if they're applied consistently, and consistency requires either constant vigilance or automation. I wanted to find out whether I could move my team's logging rules out of a document and into the tool itself, so that Claude would apply them automatically, every time, without being asked. Two Mechanisms Worth Knowing Claude Code offers two complementary ways to encode behaviour: ...

AWS Summit London 2026: And now for something a bit different.

I always look forward to the AWS Summit. It’s a great opportunity to learn what AWS, and the engineers who use it, are up to, and to catch up with my colleagues. This year, though, turned out to be a bit different. The first year I attended, I skipped the keynote entirely and spent the time in the AWS labs instead. Last year I did go to the keynote, and wished I hadn’t. This year I attempted to do both, but it didn’t really work. I managed just one very simple lab before I had to leave for the keynote. Although I did manage to get to the Red Hat stand early and be the first to get an actual red hat! Although I did have to carry it around all day and all the way back to Norwich that evening. One of the main issues is the size of ExCeL. It’s big. I mean really big. You may think it’s a long way down the street to the chemist, but that’s peanuts to ExCeL. It’s a long way from anywhere to anywhere else. Poor Hitchhiker’s Guide to the Galaxy references aside, many things, inc...

Log Judiciously

Judiciously: With good judgement. Logging is one of the simplest things a developer can do, and one of the easiest things to get wrong. A single misplaced log line can be harmless, but a pattern of careless logging turns into noise, confusion, and even security risk. The challenge isn’t teaching engineers how to log, it’s helping them understand why they’re logging in the first place. Here I intended to draw that distinction clearly: choosing logs that illuminate behaviour, support debugging, and reveal failures, while avoiding the chatter, duplication, and reassurance‑driven messages that bury the real signals. Finding the Line Between Useful and Noisy Teams often fall into the trap of believing that if they simply “log enough,” the rest of observability will take care of itself. It’s an appealing idea: produce a steady stream of detail, let dashboards and alerts sift through it, and assume that somewhere in the noise the truth will reveal itself. But this mindset skips th...

5 minutes with Winterfylleth (again)

I know what you’re thinking. Didn’t I do this not long ago? It’s true, I did . Less than 18 months ago in fact. And if Winterfylleth releases another album and does an album launch in the next 18 months I’ll go and do it all again. I left work at 2pm, got the train to London, the Underground to Cambden and spent all of five minutes with the band. I had the latest album signed - which I have twice now, on CD and on vinyl which I collected from Raven Records this evening - my ARD (mark Deeks' band) CDs and record signed, and all my Necronautical (Rust Ob Sun's band) CDs signed. They all did the Metal pose, I see them do on social media, with me. They were all very accommodating, which made my week and is why I go! Mark Deeks was there this time, and it was great to meet him in person after much messaging on social media. It was good to meet Rust Ob Sun for the first time too! His Facebook posts are great. In a flash it was over and I was heading back to Norwich, via a few ho...