gRPC over QUIC cuts seek latency 28x but lags TCP on bulk transfers

Developers testing KeibiDrop, a post-quantum encrypted peer-to-peer filesystem, evaluated replacing gRPC over TCP with gRPC over QUIC to handle IP address changes without dropping connections. Tests were conducted on a 12-core macOS laptop, a 4-core Linux VPS, and a real 72ms round-trip WAN link between Barcelona and the VPS. On the real-world link, a single QUIC stream was up to 16 times slower than TCP for bulk transfers under Wi-Fi packet loss, but random seeks completed in 109ms on QUIC versus roughly 3 seconds on TCP — a 28x improvement — because each seek gets its own independent stream. A teardown deadlock caused by closing a QUIC stream concurrently with a write was identified and fixed by using a stream reset instead of a graceful close. The team settled on a hybrid design: QUIC for interactive on-demand reads where seek isolation and connection migration matter, and TCP for bulk transfers on lossy links.