TLS / SSL certificate
TLS encrypts the exchange between browser and server; the certificate proves the identity of the domain. Let’s Encrypt made encryption free and automatable — yet expiry remains the most preventable outage on the web.
In practice
The operational standard: automatic issuance, scheduled renewal, service reload at the end of each cycle, expiry monitoring. An expired certificate does not degrade — it cuts access with a full-screen warning. Outdated protocols are disabled — TLS 1.2 minimum — without sentiment for legacy clients.