Performance
Profile First, Optimize Second
Why guessing at performance bottlenecks wastes time, and how to use profiling tools to find what actually needs fixing before you touch the code.
Performance
Caching Strategies: Where to Cache and What to Invalidate
Caches speed things up until they serve stale data. Understanding the tradeoffs at each caching layer - and how invalidation actually works - is what keeps them from becoming bugs.