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# Performance Rules for Fasten

## Targets
- Small: <100ms, <10MB; Medium: <500ms, <50MB; Large: <2s, <200MB; XL: <10s, <500MB.
- Lexer: >1MB/s; Parser: >500KB/s; Optimizer: >2MB/s; Codegen: >5MB/s.
- Cold start <50ms; base memory <5MB.

## Benchmarking
- Use provided benchmark framework; warmup, multiple iterations, throughput checks.
- Assert performance targets in tests; fail on regression >10%.

## Memory
- Use ArenaAllocator for temp data; Pool for frequent allocations.
- Profile memory; zero tolerance for leaks; peak usage <2x input size.

## Optimization
- Minimize allocations in hot paths; use stack allocation when possible.
- Profile before optimizing; document all optimizations.
- Use efficient data structures (interning, compact AST).

## Monitoring
- Collect and log metrics (time, memory, compression ratio).
- Alert on slow bundling, high memory, poor compression.
- Run performance and memory tests in CI.