Articles & Guides
Useful resources for web developers and system administrators
SSL/TLS
Let’s Encrypt ended OCSP: what to check on your server
Let’s Encrypt shut down OCSP on August 6, 2025. Check stapling, certificate metadata and nginx settings without mistaking missing OCSP for revocation.
HTTP
Keep-alive across CDN, load balancer, nginx and app
A mismatched idle timeout across proxies can reset reused connections and sometimes surface as 502. Trace the connection owner, logs and timeout settings.
SSL/TLS
curl TLS errors 35 and 60: diagnosis and the legacy code 51
Reproduced curl errors 35 and 60 for TLS negotiation, expired certificates and hostname mismatches. Learn why legacy code 51 is absent from current curl docs.
SSL/TLS
ACME HTTP-01 vs DNS-01 vs TLS-ALPN-01: choose a challenge
Compare ACME HTTP-01 on port 80, DNS-01 with TXT, and TLS-ALPN-01 on port 443. Choose a challenge for wildcard certificates, proxies and renewal.
HTTP
HTTP 500 vs 502 vs 503 vs 504: Find the Failing Hop
Distinguish HTTP 500, 502, 503 and 504 across an edge, proxy and app. A local two-hop lab shows which component emitted each code and where to check logs.
HTTP
curl Timing Breakdown: DNS, TCP, TLS, TTFB and Total Time
Use curl -w to locate slow DNS, TCP, TLS, first-byte and download phases. Three measured sites show why timing fields are cumulative and redirects need care.
DNS
CNAME at the Apex: ALIAS, ANAME and Flattening at 8 DNS Hosts
Compare apex ALIAS, ANAME and CNAME flattening at 8 DNS hosts. Direct dig queries verify A and AAAA answers, mail records, and delegation before migration.