performancelisted

# Performance Use this skill when work involves latency, throughput, resource usage, query efficiency, rendering cost, memory pressure, or scaling bottlenecks. This skill is technology agnostic. ## Measure First Do not optimize solely from intuition. Identify: - the slow operation - current baseline - dominant cost - expected improvement - acceptable tradeoffs Use measurements appropriate to the system. ## Common Bottlenecks Investigate relevant: - repeated database queries - N+1 access - unnecessary network calls - repeated computation - inefficient algorithms - excessive serialization - large payloads - blocking I/O - unnecessary rendering - memory growth - contention - cache misses - excessive file operations Do not assume the database is always the bottleneck. ## Database Performance Consider: - query count - query plans - indexes - join behavior - selected columns - pagination - batch operations - eager/bulk loading - connection usage Add indexes based on actual query patterns. ## Caching Cache when: - computation or retrieval is meaningfully expensive - reuse is likely - consistency requirements are understood Define: - cache key - lifetime - invalidation - ownership - failure behavior Do not add caching merely to hide an inefficient design without understanding correctness implications. ## Memory Avoid loading unbounded datasets into memory. Prefer: - streaming - chunking - pagination - iterators - bounded batches when processing large data.