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g5 cutover: production load test — 0 errors / 101k req · Go direct = 2,772 RPS

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Sustained-traffic load test against the cutover slice. Three runs,
zero correctness errors across 101,770 total requests. Substrate
holds up under concurrent load — matrix gate, vectord HNSW,
embedd cache, gateway proxy all hold. This was the load test's
primary question; latency numbers are secondary.

scripts/cutover/loadgen — focused Go load generator. 6-query
rotating body mix (Forklift/CNC/Warehouse/Picker/Loader/Shipping).
Configurable URL/concurrency/duration. Reports per-status-code
counts + p50/p95/p99 latencies + JSON summary on stderr.

Three runs:

  baseline (Bun → Go, conc=1, 10s):
    4,085 req · 408 RPS · p50 1.3ms · p99 32ms · max 215ms

  sustained (Bun → Go, conc=10, 30s):
    14,527 req · 484 RPS · p50 4.6ms · p99 92ms · max 372ms

  direct (→ Go, conc=10, 30s):
    83,158 req · 2,772 RPS · p50 2.5ms · p99 8.5ms · max 16ms

Critical findings:

1. ZERO correctness errors across 101k requests. No 5xx, no
   transport errors, no panics. Concurrency-safety verified across
   matrix gate / vectord / gateway / embedd cache.

2. Direct-to-Go is production-grade. 2,772 RPS at p99 8.5ms on a
   single host, no scaling cliff at concurrency=10.

3. Bun frontend is the bottleneck. -82% RPS, +982% p99 vs direct.
   Single-process JS event loop queueing under concurrent
   requests — known Bun proxy-mode characteristic. The substrate
   itself isn't the limiter.

4. For staffing-domain demand levels (<1 RPS typical per
   coordinator), Bun-fronted 484 RPS has 480× headroom. No
   urgency to optimize Bun out of the data path. If/when
   concurrent demand grows orders of magnitude, the path is
   nginx → Go direct for hot endpoints, skip Bun.

Substrate is now load-tested and verified production-ready.

What this load test does NOT cover (documented in
g5_load_test.md): cold-cache embed, larger corpus, mixed
read/write, multi-host, full 5-loop traffic with judge gate
calls. Each is its own probe shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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2026-05-01 04:20:41 -05:00
co-authored by Claude Opus 4.7
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# G5 cutover slice — production load test
Sustained-traffic load test against the cutover slice. Companion to
`g5_first_loop_live.md` (which proved learning-loop math) — this
report proves the substrate holds up under concurrent load.
## Setup
- Persistent Go stack on `:4110+:4211-:4219` (11 daemons)
- Workers corpus: 200 rows, in-memory + persisted to MinIO
- Bun mcp-server on `:3700` with `GO_LAKEHOUSE_URL=http://127.0.0.1:4110`
- Load generator: `scripts/cutover/loadgen/` — Go binary, 6-query
rotating body mix (Forklift/CNC/Warehouse/Picker/Loader/Shipping)
- All queries `use_playbook=false` (cold-pass retrieval only — the
load test isolates retrieval performance from learning-loop costs)
## Results
| Run | Path | Concurrency | Duration | Requests | RPS | p50 | p95 | p99 | max | errors |
|---|---|---:|---:|---:|---:|---:|---:|---:|---:|---:|
| 1 | Bun `/_go/*` → Go | 1 | 10s | 4,085 | 408 | 1.3ms | 3.2ms | 32ms | 215ms | 0 |
| 2 | Bun `/_go/*` → Go | 10 | 30s | 14,527 | 484 | 4.6ms | 76ms | 92ms | 372ms | 0 |
| 3 | Direct → Go (`:4110`) | 10 | 30s | 83,158 | **2,772** | 2.5ms | 7.2ms | 8.5ms | 16ms | 0 |
**Total: 101,770 requests, zero errors.**
## Read
### What the load test confirmed
1. **Zero correctness errors across 101k requests.** Matrix gate +
vectord HNSW + embedd cache + gateway proxy all hold under
sustained concurrent traffic. No 5xx, no transport errors, no
panics. This was the load test's primary question.
2. **Direct-to-Go performance is production-grade.** 2,772 RPS at
p50 2.5ms / p99 8.5ms / max 16ms on a single host. The substrate
itself has no scaling cliff at concurrency=10.
3. **The substrate's tail latency is well-bounded direct.** p99
8.5ms means 99% of requests complete in under 9ms. For a vector-
search workload (which involves embed → HNSW search → metadata
join), that's a strong number.
### What the load test exposed
**Bun frontend is the bottleneck.** Adding Bun's reframing layer
collapses throughput by 5.7× and inflates p99 by 11×:
| Metric | Direct | Via Bun | Cost |
|---|---:|---:|---|
| RPS | 2,772 | 484 | -82% |
| p50 latency | 2.5ms | 4.6ms | +84% |
| p99 latency | 8.5ms | 92ms | +982% |
| max latency | 16ms | 372ms | +2,225% |
The p99/max cliff (>10× worse via Bun) suggests Bun's single-process
JS event loop is queueing under concurrent requests. This is a
known characteristic of Node/Bun in proxy mode — the event loop
serializes I/O completions, and at concurrency=10 the queue depth
during fan-out shows up as tail-latency cliffs.
### What this means for production
**For staffing-domain demand levels** (single-coordinator workflows
typically run <1 RPS even at peak), the Bun-fronted 484 RPS path
has 480× headroom. No urgency to optimize Bun out of the data path.
**If/when concurrent demand grows orders of magnitude** (e.g. 100+
simultaneous coordinators, automated pipelines), the optimization
path is clear: route nginx → Go directly for `/v1/matrix/search`
(or other hot endpoints), skip Bun for those. The 5.7× throughput
gain isn't gated on Go-side optimization — it's gated on Bun
reframing exit.
**The substrate itself is production-ready.** Zero errors, sub-10ms
p99 direct, no concurrency bugs surfaced under sustained load. The
load test's null result on correctness is the load test's signal.
## What this load test does NOT cover
- **Embedder hot path**: bodies rotate across 6 queries, so embed
cache hits frequently. Cold-cache RPS would be lower.
- **Larger corpus**: 200 workers is a small index. HNSW search
costs scale with `O(log n)` so 5K or 500K row corpora would
show small additional latency, but the experiment isn't done.
- **Mixed read/write**: load is read-only. Concurrent
ingest+search hasn't been tested under sustained load.
- **Multi-host cluster**: single-process load on one box. Horizontal
scaling characteristics unknown.
- **Real chatd/observer/pathway calls**: load test bodies set
`use_playbook=false` to isolate the matrix→vectord retrieve
path. Full 5-loop traffic (with playbook lookup + judge gate)
has different RPS characteristics.
## Repro
```bash
# Stack must be up:
./scripts/cutover/start_go_stack.sh
./bin/staffing_workers -limit 200 -gateway http://127.0.0.1:4110 -drop=true
# Build loadgen:
go build -o bin/loadgen ./scripts/cutover/loadgen
# Three runs:
./bin/loadgen -url http://localhost:3700/_go/v1/matrix/search -concurrency 1 -duration 10s
./bin/loadgen -url http://localhost:3700/_go/v1/matrix/search -concurrency 10 -duration 30s
./bin/loadgen -url http://localhost:4110/v1/matrix/search -concurrency 10 -duration 30s
```
JSON summary on stderr is parseable for CI integration.