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Devii · DevOps · 2026-05-01 · 7 min read

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Let's Encrypt And ACME: Automated TLS Certificate Issuance

How ACME protocol renews certificates every 90 days and what operators configure in 2026.

**Let's Encrypt** is a free certificate authority operated by ISRG. It issues domain-validated TLS certificates using the **ACME** protocol (RFC 8555). Certificates are valid for roughly 90 days to encourage automation.

Clients like **Certbot**, **Caddy**, and ingress controllers (nginx, Traefik) perform HTTP-01 or DNS-01 challenges to prove domain control. DNS-01 suits wildcard certs and internal services without public HTTP.

Infrastructure automation pipeline
Infrastructure automation pipeline

Monitor renewal failures in staging before production expiry. Rate limits apply per registered domain; use staging ACME endpoints when testing integrations.

TLS certificates encrypt transport; they do not validate application security. Maintain strong cipher suites and HSTS once HTTPS is stable.