Backend performance toolkit that keeps APIs responsive

Squeezing speed from servers is easier when you layer simple tools instead of giant rewrites.

Tools I reach for

• Redis for request-scoped caching and rate limits with TTLs you can tune live.
• BullMQ or Celery for background work so web threads stay lean.
• pg_stat_statements to find slow SQL without guesswork.
• k6 for load tests you can run locally before stressing production.
• Flamegraphs from py-spy or 0x to spot hot paths.

k6 run smoke.js --vus 20 --duration 2m
redis-cli monitor | head -n 20

Define an SLO (p95 under 300ms, error rate < 0.5%) and review it weekly; tools only matter if they move those numbers.