TLS and mTLS Fundamentals#

TLS (Transport Layer Security) encrypts traffic between two endpoints. Mutual TLS (mTLS) adds a second layer: both sides prove their identity with certificates. Understanding these is not optional for anyone building distributed systems — nearly every production failure involving “connection refused” or “certificate verify failed” traces back to a TLS misconfiguration.

How TLS Works#

A TLS handshake establishes an encrypted channel before any application data is sent. The simplified flow: