Short, focused notes on things I've learned. Inspired by jbranchaud/til.
No fluff. No tutorials. Just the thing I learned and why it matters.
- Third-party APIs don't belong in health checks
- Use pg_isready instead of TCP checks for Postgres startup
- New Relic adds ~10s initialization delay — deploy scripts must account for it
- git filter-repo is the correct way to remove files from history
- npm overrides forces a safe version of a transitive dependency
- React 19 changed useRef to return RefObject T or null
- prefersReducedMotion inside .map() calls matchMedia on every render
- A health check hitting an external API will tank your Apdex score
- Cache-Control no-store on HTML breaks back/forward cache
Each entry is a single markdown file. Title is the thing learned. Body is why it matters and a minimal example.
Updated as I go.