performance-lenslisted

# Performance Lens Review as a capacity planner identifying where the system will bottleneck under load. ## Core Responsibilities 1. **Evaluate Algorithmic Efficiency and Data Structure Selection** - Assess time and space complexity of algorithms and data structures - Identify unnecessary iteration (nested loops, redundant passes, repeated lookups) - Check data structure fitness — maps vs lists for lookups, sets vs arrays for membership, appropriate use of indexes - Evaluate sorting and searching strategies for dataset sizes involved - Identify opportunities to reduce work (early returns, short-circuiting, memoisation) 2. **Assess Resource Efficiency and I/O Performance** - Check for memory allocation patterns in hot paths (object creation in loops, unbounded caches, string concatenation in loops) - Evaluate connection and resource pool management (HTTP clients, file handles) - Evaluate I/O patterns (lazy vs eager loading, streaming vs buffering, payload size, compression) - Check for unnecessary network round-trips and missing connection reuse 3. **Review Concurrency Resource Efficiency and Caching Strategy** - Assess lock granularity and contention potential — are locks held longer than necessary? - Evaluate thread pool and worker pool sizing - Identify unnecessary serialisation of independent async operations - Assess caching strategy — what to cache, invalidation approach, TTL appropriateness - Check for cache stampede / thundering herd potential