Explore micro-optimization techniques for critical path performance in Scala applications during this conference talk from Scala Days 2023 Seattle. Delve into the fundamentals of JVM, hardware, and Scala compiler operations to write dramatically faster code without sacrificing functionality. Learn about physical factors, layers of abstraction, and the characteristics of slow and fast code. Discover pro tips for implementing IO, measuring performance with SBT and JMH, and conducting micro benchmarks. Examine allocation-free stacks, continuation stacks, dynamic arrays, and array operations. Understand the intricacies of micro benchmarks and their potential pitfalls. Investigate optimization strategies, including encoding results, pattern matching, if-else statements, deftag, and invoke virtual. Gain insights into achieving faster performance with practical examples and key takeaways for effective micro-optimization in Scala and JVM-based applications.