This recounting by Max Bernstein details a real-world performance optimization saga from developing a custom Python runtime, where a seemingly innocuous string function bottlenecked Django performance. The analysis reveals how a naive Python implementation of str.rpartition led to excessive, costly UTF-8 indexing operations, emphasizing the need to look beyond surface-level profiler results to find the true cause of slowdowns.
https://bernsteinbear.com/blog/silly-perf/