Dive into a comprehensive 3-hour workshop from JuliaCon 2021 focused on improving package development in Julia. Learn about compiler specialization, dispatch, backedges, invalidation, and precompilation. Explore tools like JET, SnoopCompile, and Cthulhu to detect, diagnose, and fix issues in package implementation. Gain insights into reading lowered and typed code, catching errors and inference failures, and generating precompile directives. Aimed at experienced Julia developers, this workshop provides practical techniques to enhance package quality, streamline design, and reduce latency in the Julia programming ecosystem.