[core] Add configurable stream flush interval per world#1533
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Allow non-Vercel world implementations to override the 10ms stream write buffer flush interval. Backends with sub-millisecond writes (Redis, local filesystem) can set a lower value or 0 for immediate flushing, reducing end-to-end stream latency. Closes #1517 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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📊 Benchmark Results
workflow with no steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express workflow with 1 step💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express workflow with 25 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.race with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express Promise.race with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express Promise.race with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 25 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 25 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Stream Benchmarks (includes TTFB metrics)workflow with stream💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) stream pipeline with 5 transform steps (1MB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) 10 parallel streams (1MB each)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express fan-out fan-in 10 streams (1MB each)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) SummaryFastest Framework by WorldWinner determined by most benchmark wins
Fastest World by FrameworkWinner determined by most benchmark wins
Column Definitions
Worlds:
❌ Some benchmark jobs failed:
Check the workflow run for details. |
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🧪 E2E Test Results❌ Some tests failed Summary
❌ Failed Tests▲ Vercel Production (1 failed)nextjs-turbopack (1 failed):
🌍 Community Worlds (61 failed)mongodb (3 failed):
redis (2 failed):
turso (56 failed):
Details by Category❌ ▲ Vercel Production
✅ 💻 Local Development
✅ 📦 Local Production
✅ 🐘 Local Postgres
✅ 🪟 Windows
❌ 🌍 Community Worlds
✅ 📋 Other
❌ Some E2E test jobs failed:
Check the workflow run for details. |
VaguelySerious
commented
Apr 3, 2026
VaguelySerious
commented
Apr 3, 2026
Co-authored-by: Peter Wielander <mittgfu@gmail.com> Signed-off-by: Peter Wielander <mittgfu@gmail.com>
VaguelySerious
commented
Apr 3, 2026
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
TooTallNate
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Apr 6, 2026
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LGTM — this is a clean, focused change and the behavior is exactly what #1517 asked for.
What I checked:
WorkflowServerWritableStreamnow correctly usesworld.streamFlushIntervalMs ?? STREAM_FLUSH_INTERVAL_MSso worlds can opt in without changing defaults.streamFlushIntervalMs = 0works as intended (??preserves 0 instead of falling back).streamFlushIntervalMsis optional onStreamer, so existing custom worlds remain source-compatible.- world-local and world-postgres thread the option through config and expose it on the world object; world-vercel stays on default behavior.
- New tests cover 0, custom non-zero, and undefined fallback cases.
One small non-blocking nit: in createLocalWorld, storage is currently created twice (const storage = ... and ...createStorage(...)). It works, but ...storage would avoid duplicate wrapper allocation and keep references consistent. Not blocking for merge.
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Summary
streamFlushIntervalMsoptional property to theStreamerinterface in@workflow/worldWorkflowServerWritableStreamreads this from the world, falling back to the existing 10ms defaultworld-localandworld-postgresexpose it as a config option;world-vercelalways uses the defaultCloses #1517
Test plan
streamFlushIntervalMs = 0(immediate flush)🤖 Generated with Claude Code