Practical writing for engineers who debug production. No "in today's digital landscape", no listicles — just the technical detail you needed at 2am.
PTR records map an IP back to a name. They look like trivia until your outbound email starts hitting spam folders. Here is what PTR proves, what it does not, and how to set it.
The hardest DNS failures are the ones that work most of the time. Here is a debugging flow that catches the seven causes of intermittent resolution errors.
Internal users get an internal IP for the same hostname; external users get the external one. Useful for keeping URLs portable across networks, and a great way to break a network if done wrong.
Both encrypt DNS between you and the resolver. One is indistinguishable from web traffic on port 443; the other has its own port. Why your operations team probably has an opinion.
A wildcard covers any subdomain at one level. A SAN cert covers an explicit list. The choice is operational, not cryptographic — here are the tradeoffs that matter.
Cache poisoning has been a known DNS attack for two decades. DNSSEC is the official answer. Why adoption is so uneven, and what protection you actually get.
ACME is a four-message protocol that automates everything a CA used to require humans for. Here is the mental model that lets you debug any ACME failure in five minutes.
HSTS is a one-line response header that locks browsers into HTTPS for your domain. The preload list takes that commitment further — and the only way out is a year-long opt-out process.
HTTP/3 swaps TCP for QUIC. The handshake is faster, head-of-line blocking is gone, and your CDN is probably already speaking it. But for plenty of workloads, HTTP/2 is still the right call.
OCSP lets clients check whether a cert has been revoked. Stapling moves that check from the client to the server. Why this matters, how it works, and what breaks when it fails.