QUIC

QUIC, standardized as RFC 9000, is a general-purpose transport protocol that runs over UDP and folds connection setup, multiplexing, and TLS 1.3 encryption into a single, low-latency handshake. Originally developed at Google and then finalized by the IETF, it was designed to fix long-standing pain points in TCP - head-of-line blocking, slow connection establishment, and mid-path ossification. It is the transport foundation of HTTP/3.

• UDP-based - Built on UDP so the protocol can evolve in user space instead of being frozen into operating-system TCP stacks.
• Built-in TLS 1.3 - Encryption is not optional; security is part of the transport rather than a layer bolted on top.
• Stream multiplexing - Independent streams over one connection eliminate the head-of-line blocking that hurts HTTP/2 over TCP.
• Low-latency handshakes - Combined transport and cryptographic setup, with 0-RTT resumption for returning connections.
• Connection migration - A connection ID lets a session survive a network change, such as moving from Wi-Fi to cellular.

For API operations QUIC matters as the layer underneath HTTP/3, where faster handshakes and stream multiplexing translate into lower latency and better resilience for high-volume API traffic, especially over mobile and lossy networks. Most API teams adopt it not by implementing QUIC directly but by enabling HTTP/3 at their gateway, CDN, or load balancer. As agent-driven systems generate ever more chatty, latency-sensitive API calls, an efficient encrypted transport like QUIC becomes an increasingly practical part of the stack.