Benchmark hot-path optimizations

For code on frequently executed paths (request handling, routing, serialization, middleware), base optimization decisions on actual benchmarks rather than assumptions, and avoid introducing redundant work. Concretely:

• Measure before and after any performance-motivated change using a tool like mitata or console.time, and include the comparison in the PR description when the change trades readability/DRYness for speed.
• Hoist invariant computations out of functions that run per-request/per-call. For example, compile regular expressions once at module scope instead of inside a function: ```ts // Bad: regex is recompiled on every call const parseValue = (value: string) => value.split(/;(?=(?:(?:[^”]”){2})[^”]*$)/)

// Good: regex compiled once const SPLIT_REGEX = /;(?=(?:(?:[^”]”){2})[^”]*$)/ const parseValue = (value: string) => value.split(SPLIT_REGEX) ```

• Avoid unnecessary allocations/branches on the fast path. Prefer cheap guard checks (e.g. /%/.test(str) before decoding, str.includes(...) before a replace) over always running the expensive operation, and prefer constructing objects (e.g. new Response()) with the minimal set of options needed.
• It’s acceptable to keep similar-looking logic duplicated across call sites (e.g. JSX attribute stringification) rather than unifying it behind a shared abstraction, if sharing it would add branching/argument overhead to a hot loop. Prioritize per-call-site optimization over DRY in these cases.
• When a native/built-in API (e.g. Response.json()) is simpler and measurably at least as fast as a hand-rolled equivalent, prefer it.
• Don’t touch or “simplify” already-optimized code outside the scope of the current change, especially if it doesn’t move the needle or risks regressing a hot path; keep optimization-focused PRs narrowly scoped and justified by data.

The goal is to make performance-sensitive changes deliberate, measured, and scoped to the code that actually executes on every request, rather than guessing or optimizing cold paths at the expense of clarity.