Step-by-step playbooks for when things go sideways. Interactive checklists with copy-paste commands.
Diagnose and fix Nginx 504 timeout errors caused by slow backend responses. Covers response time measurement, backend diagnostics, timeout tuning, and database query analysis.
Troubleshoot PostgreSQL connection failures. Covers service status, listen address configuration, pg_hba.conf authentication rules, connection limits, and restart procedures.
Diagnose and fix replication lag between MySQL/MariaDB primary and replica servers. Covers IO/SQL thread status, binary log analysis, and safe error recovery.
Diagnose and fix OOM errors in Redis. Covers reading memory stats, finding big keys, choosing a sane eviction policy, and spotting fragmentation before it triggers a kernel OOM kill.