The text delves into the intricacies of optimizing TypeScript's type-checking performance, a challenging aspect for developers often leading to issues like sluggish IDE responsiveness and compiler crashes. It describes the complexity of troubleshooting type-checking issues, given that traditional debugging techniques are ineffective since type checking occurs at build time. The article shares insights from a recent performance regression faced by the authors due to changes in TypeScript 5.3's type inference algorithm, which significantly impacted their test suite and necessitated devising a strategy for measuring and improving type inference performance. By employing tools like --extendedDiagnostics, --generateTrace, and the @arktype/attest package, the authors were able to quantify type-checker workload through metrics such as type instantiations, ultimately developing a method dubbed "BAM" (Branch, Adjust, Measure) to iteratively refine code for better performance. The guide also offers general advice for optimizing TypeScript type performance, including using interfaces over intersections, naming conditional types, and considering the order of conditionals, while advocating for the development of more advanced performance tools to aid in this endeavor.