HTTP/3 and QUIC
Slap yourself if
You think HTTP/3 is just HTTP/2 over UDP or believe QUIC magically removes all network latency.
Why this exists
Because HTTP/3 is often sold as a free performance upgrade, while teams miss its real benefits, new failure modes, and the operational complexity it introduces.
Mental model
QUIC is a transport redesign that trades TCP’s global ordering and kernel ownership for user-space control, multiplexed streams, and faster recovery — at the cost of complexity and new edge cases.
- QUIC runs over UDP and implements reliability, congestion control, and TLS in user space.
- HTTP/3 multiplexes streams without head-of-line blocking at the transport layer.
- Connection setup combines transport and encryption handshakes.
- Packet loss affects individual streams instead of stalling the entire connection.
- Assuming HTTP/3 always outperforms HTTP/2.
- Ignoring middlebox and firewall interference with UDP.
- Misattributing gains to HTTP semantics instead of transport behavior.
- Forgetting fallback behavior when QUIC is unavailable.
HTTP/3 uses QUIC over UDP to avoid transport-level head-of-line blocking and reduce handshake latency, while shifting transport complexity into user space.
- Calls it HTTP/2 over UDP.
- Claims it eliminates latency.
- Ignores congestion control.
- Does not mention fallback to HTTP/2.
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