System Design
Two million games, one running clock
Plate two: two players sharing one truth while the clock runs, and why the bravest thing a real-time system can do is stop.
Architecture
Security
Securing GenAI at enterprise scale
Large language models are rarely the weakest part of a GenAI system. The prompts, permissions, tools and people wrapped around them usually are.
Architecture
Answering questions with MCP
This site now answers questions over MCP through a tool called `ask_matt`. It quotes from published articles, hands over the hand-kept numbers when a question wants one, cites everything, and refuses the rest. The refusal took the most design effort.
Architecture
The anatomy of a resilient system
Servers fail every day. Whether that becomes an outage depends far more on the organisation than the infrastructure.
Architecture
The traceability problem
Most engineering systems are built to answer what happened. The harder question, the one that surfaces at the worst possible moment, is who changed what, when, why, and whether they should have.
Engineering Leadership
AI doesn't change Conway's law
Every technology generation promises to transform how software gets delivered. Most of them eventually rediscover that organisational structure shapes the outcome far more than the tools the engineers happen to be holding.
Architecture
Your AI doesn't need another API, it needs a toolbox
Why Model Context Protocol matters less because of the protocol itself and more because it solves a problem every engineering organisation eventually encounters.
System Design
Designing a URL shortener for its worst day
Resilience is a design input, not a deep dive at the end. The first in a series: the smallest system everyone knows, designed around the question of what is allowed to die.
Payments
Moving money is hard
Most software engineers think a payment is a database transaction. The payments industry has spent decades proving otherwise.
Security
Secrets are everywhere
Most security incidents don't begin with sophisticated attackers. They begin with credentials sitting somewhere they shouldn't.
Computer Science
Building a double-entry ledger in 200 lines
Every system that tracks value eventually needs a ledger, and most start with a balance column and a sense of optimism. The fix is double-entry bookkeeping: five hundred years old, and small enough to build in an afternoon.
Engineering Leadership
Why most technical debt is really organisational debt
Code rarely becomes hard to maintain because engineers wanted it that way. More often the architecture is just a faithful record of the incentives, constraints and decisions of the organisation around it.
Platform Engineering
Building a desktop platform is like building an operating system
Most engineers think desktop platforms are about windows and toolbars. The hard parts are identity, communication, deployment, versioning and convincing hundreds of applications to coexist without setting fire to each other.
Computer Science
Building a trading exchange in 200 lines
Modern financial exchanges move billions of dollars a day, yet the core matching engine comes down to a handful of data structures and a few unglamorous rules.
JavaScript
Most JavaScript performance problems aren't JavaScript problems
After enough profiling sessions you start to realise the language is rarely the bottleneck. Our assumptions usually are.
Architecture
Caching is easy until it isn't
Most caching strategies look brilliant during architecture reviews and become considerably less impressive the first time stale data reaches production.