feat(evaluation): pre-evaluate static flags for host-side caching#68
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…e caching Static flags (no targeting rules) and disabled flags always return the same result regardless of context. Pre-evaluate them during update_state() and include results in the response so hosts can cache them and skip the WASM boundary entirely. Rust: UpdateStateResponse gains a preEvaluated map populated by a new pre_evaluate_static_flags() helper in FlagEvaluator::update_state(). Java: FlagEvaluator stores the map in a volatile cache that is replaced atomically on each updateState(). evaluateFlag() checks the cache first and returns immediately on hit, avoiding all WASM overhead for simple flags (~4.4µs → ~0.02µs). Closes #60 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
update_state()and return results in the responseFlagEvaluatorcaches these results and returns them directly fromevaluateFlag(), skipping the WASM boundary entirelyMotivation
JMH benchmarks showed a ~200x latency gap for simple flags: native JsonLogic at 0.022 µs/op vs WASM at 4.41 µs/op. The overhead comes from JSON serialization across the WASM boundary — but static flags don't need any of that, they always return the same result.
Changes
Rust
src/model/mod.rs: Addedpre_evaluated: Option<HashMap<String, EvaluationResult>>toUpdateStateResponsesrc/evaluator.rs: Addedpre_evaluate_static_flags()that evaluates all static/disabled flags with empty context duringupdate_state()Java
UpdateStateResult.java: AddedpreEvaluatedmap fieldFlagEvaluator.java: Addedvolatilecache populated onupdateState(), checked first inevaluateFlag()— cache hit skips WASM entirelyREADME.md: Updated Performance section with benchmark comparison tablesExpected performance impact
Test plan
cargo test— all Rust tests passcargo clippy -- -D warnings— cleancargo fmt -- --check— clean./mvnw test— all 30 Java tests pass (existing tests exercise static flags via cache)Closes #60
🤖 Generated with Claude Code