Added new post for Newsletter #65 with summaries of articles on scaling engineering teams, AI usage pitfalls, major infrastructure outages, Linux boot process, build system tradeoffs, Claude Code usage, and tinkering. Updated the introduction in Newsletter #64 to fix links and formatting.

Added a new newsletter post for 2025-12-06 covering topics such as caching, Big O notation, consistent hashing, Linux thread management, advice for principal engineers, Java performance, programming language insights, and bonus technical illustrations.