We run the TechEmpower Framework Benchmarks: open-source, reproducible web framework benchmarks across hundreds of implementations.

Between Round 22 and Round 23, our spring-mongo query test dropped from ~5,900 req/s to 583. That's weird, what gives?

We worked with MongoDB's performance team and Intel to trace it to two root causes:

1. TCMalloc's per-CPU memory pools behaving poorly inside Docker containers 2. Connection pool sizing and driver config not tuned for the hardware

After MongoDB submitted fixes, the query test went from 583 to 14,200 req/s. The db test hit 205k (up from 68k). Fortune went from 59k to 188k.

All benchmark code and results are open source: https://github.com/TechEmpower/FrameworkBenchmarks