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Performance

Current public performance claims and runtime knobs are listed here. Benchmark history belongs in the benchmark repository or changelog, not in maintained docs.

Public Numbers

Measured on Apple M4 Pro with ReleaseFast builds:

Metric Current claim
Cold-start floor about 3.5 ms
Typical cold start about 7-15 ms, host-load dependent
Baseline RSS after first response about 13 MB
HTTP throughput on trivial JSON handler about 112k req/s
Deployed local binary about 4.8 MB

Cold start is measured from process launch to first complete HTTP response for zigttp serve -e <handler>. Treat it as a distribution: scheduling jitter and host load move the tail.

Run the in-repo benchmark suite with:

zig build bench
zig build bench-check

What Affects Latency

  • Build-time precompile with zig build -Dhandler=handler.ts or zigttp build embeds handler bytecode and removes parse/codegen work from startup.
  • -n controls isolated runtime count. The default is derived from CPU count and clamped to 8-128.
  • -m sets a per-runtime allocator ceiling. The default is no explicit limit.
  • zigttp:fetch, zigttp:service, zigttp:io, durable workflows, and WebSocket paths depend on external systems and runtime flags.
  • Handlers proven deterministic and read-only can serve cached GET/HEAD responses from Zig memory.

Engine Optimizations

The current runtime includes:

  • hidden-class shapes for request, response, and object literals;
  • polymorphic inline caches for property access;
  • binary search for larger object property tables;
  • lazy string hashing and pre-interned HTTP atoms;
  • type feedback for JIT decisions;
  • per-context native JIT code cap with full-context eviction at compile safe points;
  • specialized bytecode for type-directed boolean and comparison paths;
  • request-scoped allocation with bulk reset.

These details are implementation notes, not public API. Use the benchmark commands above when changing engine or runtime hot paths.

Deployment Notes

zigttp deploy produces a local self-contained binary under .zigttp/deploy/<project-name>. Run multiple instances behind a reverse proxy or platform load balancer for higher throughput. A standalone zigttp serve process should not be exposed directly without the usual network controls.

For current limits and failure behavior, see Reliability.