Python

A comprehensive performance reference for Python 3.11+ that gives Claude 42 specific optimization rules across eight categories, from critical async patterns and data structure selection down to micro-optimizations. Most useful when you're writing I/O-heavy code or need to make smart choices about collections, memory usage, and concurrency patterns. Each rule includes concrete performance impact metrics (like "2-5× faster" or "O(n) to O(1)"), so Claude can prioritize what actually matters. The focus on asyncio, connection pooling, and proper data structure selection makes this especially good for backend services and API work. It's opinionated about modern Python idioms, which means you'll get consistent recommendations but might clash if you're stuck on older patterns.