An engineering notebook. Whatever's on the workbench.

A deterministic sweep: goodput peaks at an admission limit of capacity times deadline, then collapses eight slots later.

110 rps against 100 rps of capacity drops goodput to 42 rps, and retries make it worse. A deterministic Java model.

A timeout caps p99 at 200ms yet scores the same SLI as doing nothing. A bulkhead holds 99.6% and keeps the error budget.

Five admission strategies under the same 2x overload. Token buckets hold 10ms p99; a bounded queue is the worst of both.

A closed-loop benchmark reports 10ms p99 while the service froze for 500ms. Open-loop measurement says 460ms. Same run.

ShutdownOnFailure became a Joiner and throwIfFailed disappeared. The two non-mechanical parts of our Java 25 migration.

Outcome counters per scope, propagated deadlines, bulkheads, and JFR pinning watch: four checks before trusting fan-out.

Quorum aggregation, per-tenant bulkheads, and a deadline shape that survives a slow upstream. Cancellation comes first.

Joiner scopes replace ShutdownOnFailure and scoped values leave preview. What moving Loom to Java 25 actually takes.

Adopt the stable Loom pieces now and fence preview APIs behind small helpers. Timing, not features, decides the roadmap.

Carrier counts hide millions of virtual threads, and high CPU usually means pinning. Watch that instead of pool depth.