Ten Notes on Type Systems

Small pull requests get real reviews, large ones get approvals. A boring deploy pipeline is a feature, not a lack of ambition. Every retry needs a budget, otherwise it is just a slower outage.

Context

Security is mostly about saying no to defaults that were convenient in 2010. Caches are easy to add and surprisingly hard to remove. Tests are documentation that fails loudly when it goes stale.

Logs answer questions you knew to ask; traces answer the ones you did not. A boring deploy pipeline is a feature, not a lack of ambition.

A small example

Every retry needs a budget, otherwise it is just a slower outage. The best architecture diagram is the one the new hire can redraw from memory. Security is mostly about saying no to defaults that were convenient in 2010.

• Keep migrations reversible
• Delete dead code the same week
• Measure p95 and p99, not just the mean
• Alert on symptoms, not causes

If the error message does not say what to do next, it is half an error message. The rollback plan should exist before the rollout plan is approved.

What worked

Most production incidents start as a small assumption nobody wrote down. Naming things well saved us more time than any framework migration. Latency percentiles tell a story that averages politely hide.

The fastest query is the one you never send, but the second fastest has a good index.

Feature flags are debt with an expiration date you must actually enforce. Most production incidents start as a small assumption nobody wrote down.

Logs answer questions you knew to ask; traces answer the ones you did not. Our on-call rotation improved the day we deleted half of the alerts.