Networking
Your Webhook Handler Will Be Called Twice and You Should Plan For It
At-least-once delivery means duplicates are normal operation, not an edge case. Here is how to build a handler that survives them.
Databases
Your Cache Is Serving Stale Data and the Bug Is in the Invalidation
Reading from cache is easy. Knowing when to remove something is where the bugs live, and most of them are races.
Shopify
Why Your Shopify Theme Scores 40 on Lighthouse (And the Order to Fix It In)
Most Shopify performance advice is a list of tips in no particular order. Here is how to measure first, find the actual cause, and fix things in the order that matters.
JavaScript
Debugging Slow TypeScript Builds With generateTrace
Your editor takes four seconds to show a type error and tsc takes two minutes. There is a profiler for this and almost nobody uses it.
Networking
GraphQL Returns 200 With Your Error Inside It
Every response is a success as far as HTTP is concerned. That one design decision breaks monitoring, retries, and error handling unless you plan for it.
Bug Hunt
The Bug That Only Happened on Tuesdays
A weekly export failed every Tuesday and worked every other day. Three wrong hypotheses later, the cause was a date format string nobody had looked at in four years.
Performance
How to Read a Flame Graph in Sixty Seconds
Width is time, stacking is call depth, and left to right means nothing. Once those three facts land, flame graphs become the fastest way to find a bottleneck.
Debugging
Recovering Work After a Bad git reset --hard
Your commits are almost certainly still there. Here is how reflog works, what it cannot save, and the recovery path for each case.
Networking
redirect_uri_mismatch and the Rest of OAuth Debugging
OAuth errors are unhelpful by design, because detailed errors would help attackers too. Here is how to work out what is actually wrong.
AI
Testing an LLM Feature When the Output Is Different Every Time
You cannot assert equality on a model response. You can assert a lot of other things, and most teams assert none of them.
Debugging
How Breakpoints Actually Work: INT3, ptrace, and the Debugger Contract
Setting a breakpoint rewrites your program's machine code while it runs. Here is the mechanism, from the 0xCC byte up to why conditional breakpoints are slow.
Debugging
What Running Hosting Infrastructure Taught Me About Debugging
Five years of keeping other people's websites online rewired how I think about failure. Mostly by making the consequences immediate.