Start mypy with its defaults, fix what it finds, turn on check_untyped_defs, then make one module at a time strict. Every function you annotate checks every place that calls it, so start with the busiest ones.
Trace a wrong callback receiver, bind one stable listener, and verify start, stop and restart without duplicate or stale subscriptions.
Start with the recommended rules, fix what's automatic, turn noisy rules into warnings, and make CI fail only on new problems. The linter becomes useful on day one instead of ignored.
Trace a detached preview from its DOM node to an application Map, repair cleanup, and verify repeated open-and-close cycles with heap snapshots.
Measure contrast by number, run axe, and walk the keyboard focus path with a script to catch what the tool cannot see.
Install typescript-eslint on TypeScript 7, switch the rules on as warnings, count them by rule and hold the count down. After this, you can adopt type-aware linting without blocking the team for a week.
Run one slow query with EXPLAIN ANALYZE and read it with a five-question checklist: rows touched, filtered rows, estimates, loops and sort spills. After this, you can find the slow node of a plan and check your fix.
Turn on pg_stat_statements in a Docker container and list the statements that cost the most in total. After this, you know which query to tune first, and you do not have to guess.
Reproduce a deadlock between two money transfers, read the message, and fix it by locking rows in the same order. After this, you can turn a deadlock detected error into a plain wait.
Break an app on purpose and compare three health checks, then put the one that works in the Dockerfile. After this, unhealthy means the app is broken, not the check.