bitvid/weekly-perf-report-2026-02-21.md

# Weekly Performance Report — 2026-02-21

## Summary
- **Scenario:** Moderation Service lookups (Trusted Mutes).
- **Optimization:** Throttled `pruneTrustedMuteAggregates` to run at most once per minute per author.
- **Impact:** ~43% reduction in lookup latency for authors with many muters.
- **Risk:** Low. Correctness is maintained; expired mutes might persist in memory for up to 1 extra minute, which is acceptable for a 60-day window.

## Methodology
1. **Scenario Selection:** `moderationStage` in the feed engine calls `moderationService.isAuthorMutedByTrusted` for every video. Profiling revealed that `getActiveTrustedMutersForAuthor` was eagerly pruning expired mutes on *every read*.
2. **Baseline Measurement:**
   - Script: `benchmarks/moderation_service_bench.js`
   - Setup: 100 authors, 500 muters each (10% expired).
   - 10,000 read operations.
   - **Baseline:** ~39.13ms total (3.91µs/op).
3. **Optimization:**
   - Modified `js/services/moderationService.js` to skip pruning if `lastPrunedAt` was less than 60 seconds ago.
4. **Verification:**
   - Re-ran `benchmarks/moderation_service_bench.js`.
   - **After:** ~22.16ms total (2.21µs/op).
   - **Improvement:** 43% faster.
   - Ran `tests/moderation/` to ensure no regressions.

## PRs & Issues
- **PR:** (This commit) `perf: throttle trusted mute pruning`
- **Follow-ups:**
  - Consider moving pruning entirely to a background interval if the mute list grows significantly.
  - Explore caching `isAuthorMutedByTrusted` results for a few seconds in `moderationStage`.

## Commands Run
```bash
node benchmarks/moderation_stage_bench.js # Feed stage macro-benchmark
node benchmarks/moderation_service_bench.js # Service micro-benchmark
npm run test:unit:shard1 # General unit tests
node scripts/run-targeted-tests.mjs tests/moderation/*.test.mjs # Moderation tests
```