4xx Client Errors Explained: 400, 401, 403, 404 & 429
What 4xx HTTP client errors mean — 400, 401, 403, 404, 405, 408, 410, 429 — their causes, how they differ from 5xx, and how to monitor and alert on them.
May 30, 2026
10 min read
5xx Error Rate Monitoring: 500, 502, 503 Alert Guide
Track 5xx server error rates in production. Set alerts on 500, 502, 503 patterns and distinguish app bugs from infrastructure failures.
May 11, 2026
15 min read