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.
Renew an expired or expiring SSL/TLS certificate. Covers Let's Encrypt/certbot renewal, manual certificate replacement, web server reload, and auto-renewal setup.
Fix a certbot renewal that's stuck failing. Covers HTTP-01 + DNS-01 challenges, rate limits, webroot + authenticator mismatches, and getting the cert pushed to services that cached the old chain.