Envoy Upgrade Caused 20% HTTP/2 Throughput Drop: A Deep Dive

jedisct1 · x · 2026-08-05

The Apoxy team shared a post-mortem on a 20% HTTP/2 throughput drop caused by a routine Envoy proxy version bump.

Root Cause: Bisecting versions pointed to Envoy v1.34, which switched the default HTTP/2 codec from nghttp2 to Google's oghttp2. Users had previously reported 15–25% latency regressions, prompting v1.37.0 to revert the default back to nghttp2.
Technical Analysis: The post dives deep into the differences between the two codecs. It utilizes flamegraphs and benchmarks across multiple microarchitectures (Intel, AMD, AWS Graviton4, Google Axion) to investigate the performance overheads, ultimately tracing the issue down to the Huffman code hiding inside HTTP headers.

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