JoeC Field Guidehttps://joec.pw/guides/Practical infrastructure and operations guides.en-usSPF, DKIM and DMARC: troubleshooting email authenticationhttps://joec.pw/guides/spf-dkim-dmarc-troubleshooting.htmlhttps://joec.pw/guides/spf-dkim-dmarc-troubleshooting.htmlDiagnose DNS record syntax, alignment, authentication results and enforcement changes responsibly.Sun, 01 Nov 2026 00:00:00 +0000Designing a safe deployment and rollback workflowhttps://joec.pw/guides/safe-deployment-rollback.htmlhttps://joec.pw/guides/safe-deployment-rollback.htmlUse immutable releases, preflight validation, health checks and deliberate rollback verification.Sun, 01 Nov 2026 00:00:00 +0000Prometheus error rates and availability objectiveshttps://joec.pw/guides/prometheus-error-rates.htmlhttps://joec.pw/guides/prometheus-error-rates.htmlCalculate request error ratios from counters while accounting for labels, low traffic and reliability objectives.Sun, 01 Nov 2026 00:00:00 +0000PostgreSQL replication lag: what to measurehttps://joec.pw/guides/postgresql-replication-lag.htmlhttps://joec.pw/guides/postgresql-replication-lag.htmlInterpret primary-side replay metrics and standby-side receive/replay timestamps without assuming one lag signal fits all.Sun, 01 Nov 2026 00:00:00 +0000Designing a safe Linux health-check scripthttps://joec.pw/guides/linux-health-check-script.htmlhttps://joec.pw/guides/linux-health-check-script.htmlBuild read-only diagnostics for disk capacity, systemd services and host resources without changing state.Sun, 01 Nov 2026 00:00:00 +0000IPv4 subnetting: practical /31 and /32 exampleshttps://joec.pw/guides/ipv4-subnetting-31-32.htmlhttps://joec.pw/guides/ipv4-subnetting-31-32.htmlUnderstand prefix math, point-to-point /31 networks, /32 host routes and common allocation mistakes.Sun, 01 Nov 2026 00:00:00 +0000Building an incident timeline from application logshttps://joec.pw/guides/incident-timeline-from-logs.htmlhttps://joec.pw/guides/incident-timeline-from-logs.htmlNormalize timestamps, correlate evidence, record actions and distinguish facts from hypotheses.Sun, 01 Nov 2026 00:00:00 +0000HTTP security headers: what they do and do not protecthttps://joec.pw/guides/http-security-headers-explained.htmlhttps://joec.pw/guides/http-security-headers-explained.htmlReview CSP, HSTS, nosniff, framing controls and referrer policies in deployment context.Sun, 01 Nov 2026 00:00:00 +0000DNS resolution versus network connectivityhttps://joec.pw/guides/dns-resolution-vs-connectivity.htmlhttps://joec.pw/guides/dns-resolution-vs-connectivity.htmlDistinguish resolver failures, routing problems, port blocks and TLS issues using layered tests.Sun, 01 Nov 2026 00:00:00 +0000Reviewing configuration differences before deploymenthttps://joec.pw/guides/configuration-diff-deployment.htmlhttps://joec.pw/guides/configuration-diff-deployment.htmlNormalize and compare changes, avoid exposing secrets and create repeatable approval and rollback evidence.Sun, 01 Nov 2026 00:00:00 +0000Troubleshooting Cloudflare Tunnel 502, 522 and 525 errorshttps://joec.pw/guides/cloudflare-tunnel-origin-errors.htmlhttps://joec.pw/guides/cloudflare-tunnel-origin-errors.htmlLearn to separate tunnel-to-origin failures from edge-to-origin connectivity and TLS handshake errors.Sun, 01 Nov 2026 00:00:00 +0000Apache and PHP-FPM: when HTML loads but PHP failshttps://joec.pw/guides/apache-php-fpm-troubleshooting.htmlhttps://joec.pw/guides/apache-php-fpm-troubleshooting.htmlA structured approach to Apache routing, FastCGI sockets, PHP handler configuration and error visibility.Sun, 01 Nov 2026 00:00:00 +0000