Extinguishing our performance fires and rebuilding for the future

This post details significant performance improvements in Bitbucket Cloud, primarily by addressing bottlenecks in the file system layer. Key contributions include: 1. Caching packfiles for Git operations (clones, fetches) to reduce file system I/O by nearly half. 2. Implementing a custom libgit2 ODB backend with a high-performance caching layer between libgit2 and the file system, reducing throughput by over 30% for website and API traffic. 3. Optimizing diff caching by consolidating ad-hoc caching strategies, leveraging known access patterns to warm caches, and improving cache hit rates for APIs like pull request conflicts to nearly 100%. The post also outlines future investments in formalizing performance SLOs, transitioning to a new team ownership model for performance metrics, and building automation for guardrails and circuit breakers.