Achieving Sub-Millisecond Routing in Go

The Allocation Problem

Standard HTTP routers in Go allocate memory on every request. At 50,000 requests per second, the garbage collector becomes the bottleneck — not your business logic.

Profiling a production service with pprof revealed that 40% of CPU time was spent in runtime.mallocgc. Each request triggered 7 heap allocations totaling ~1 KB.

The Zero-Allocation Approach

We implemented a radix trie that operates directly on the request byte slice:

1. sync.Pool for reusable path buffers
2. Stack-allocated parameter extraction
3. Byte-slice matching — no string conversions

Results

The key insight: eliminate allocations at the hot path, and the GC stops being your enemy.