Directive's constraint engine is designed for real-time applications. These benchmarks measure every hot path.

Results

All numbers measured on an Apple M4 Max, Node.js 22, using Vitest's built-in bench API. Run pnpm bench to reproduce.

Fact Mutations

Operation	ops/sec	Latency
Single fact read	18,873,452	53ns
Single fact set	6,332,174	158ns
100 facts batched	127,486	7.8μs
100 fact reads via proxy	142,357	7.0μs

Derivations

Operation	ops/sec	Latency
Simple derivation (invalidate + read)	1,880,103	532ns
10 chained derivations	259,680	3.9μs
50 chained derivations	55,568	18μs
Invalidate 20 derivations (1 fact change)	1,490,468	671ns

Constraint Evaluation + Reconciliation

Operation	ops/sec	Latency
No-op reconcile (nothing changed)	67,379	15μs
Single constraint + resolver	56,569	18μs
10 constraints, 1 triggers	28,382	35μs
Minimal cycle (1 fact → 1 constraint → 1 resolver)	45,721	22μs
Medium system (5 facts → 3 constraints → 3 resolvers → 5 derivations)	18,780	53μs

Real-World Scenarios

Scenario	ops/sec	Latency	Description
Traffic light	27,009	37μs	9 event dispatches → 3 constraint transitions
Auth flow	35,334	28μs	login → token → profile (cascading constraints)

Head-to-Head Comparison

All libraries benchmarked side-by-side on the same machine (M4 Max, Node 22) using identical operations via Vitest bench. Run pnpm bench -- --grep Comparison to reproduce.

Single Read (ops/sec)

Library	ops/sec	Relative
Preact Signals	33,268,404	1.00x
Zustand	33,211,323	1.00x
XState	32,825,106	0.99x
Redux Toolkit	32,732,659	0.98x
MobX	23,280,113	0.70x
Directive	18,281,792	0.55x
Jotai	9,092,914	0.27x

Single Write (ops/sec)

Library	ops/sec	Relative
Preact Signals	30,237,572	1.00x
Zustand	16,601,258	0.55x
MobX	9,220,850	0.31x
Directive	7,600,237	0.25x
Redux Toolkit	2,347,409	0.08x
Jotai	2,143,979	0.07x
XState	1,247,273	0.04x

Derived/Computed Value (write + read, ops/sec)

Library	ops/sec	Relative
Preact Signals	22,684,122	1.00x
Zustand	13,012,622	0.57x
MobX	4,936,002	0.22x
Redux Toolkit	2,307,794	0.10x
Directive	2,061,300	0.09x
XState	1,252,395	0.06x
Jotai	830,972	0.04x

1,000 Write+Read Cycles (ops/sec)

Library	ops/sec	Relative
Preact Signals	83,112	1.00x
Zustand	26,609	0.32x
Directive	9,667	0.12x
MobX	9,318	0.11x
Redux Toolkit	2,460	0.03x
Jotai	1,824	0.02x
XState	1,222	0.01x

What Only Directive Can Do

The comparison above measures raw state operations. Directive is slower on pure reads/writes because every access goes through a Proxy that enables auto-tracking. But Directive is the only library that also does:

Capability	Directive	Others
Full reconcile (constraints + resolvers)	18,780/s (53μs)	–
Auth flow (3-step cascade)	35,334/s (28μs)	–
Causal debugging (`explain()`)	Yes	No
Auto-tracked derivations	Yes	Only MobX, Signals
Constraint-driven cache invalidation	Yes	No
Time-travel debugging	Yes	Only Redux (via devtools)
Zero dependencies	Yes	Only Zustand, Jotai

The trade-off: Directive's proxy overhead costs ~2x vs plain object reads, but enables auto-tracking, causal debugging, and the constraint engine – features no other library provides.

Why It's Fast

Three optimizations account for most of the performance:

Module-level __DEV__ const – V8's JIT compiler can't optimize proxy traps that contain process.env.NODE_ENV checks (treated as potentially side-effectful). Hoisting to a module-level const lets V8 compile the proxy handler to native code. This alone gave a 3.1x improvement on reads.
queueMicrotask instead of setTimeout(0) – The settle() function used setTimeout(0) to yield before checking settlement. Browsers clamp setTimeout(0) to ~1-4ms. Replacing with queueMicrotask resolves within the same microtask queue, eliminating ~1ms of scheduler latency per cycle. This gave a 23-97x improvement on reconciliation.
Fast-path trackAccess – 99% of fact reads happen outside derivation computation. An early return when trackingStack.length === 0 skips the entire tracking mechanism, saving 3 function calls per read.

Running Benchmarks

pnpm bench

Individual categories:

pnpm bench -- --grep "Fact Mutations"
pnpm bench -- --grep "Derivations"
pnpm bench -- --grep "Reconciliation"

Next Steps

Constraints – How the constraint engine works
Derivations – Auto-tracked computed values
Plugins – Performance plugin for runtime metrics