Reviews a change for performance across the whole stack — frontend bundle and render cost, backend latency and throughput, caching, and behavior under load. It's a cross-cutting perf lens, not a layer: it spots the round trip, the accidental O(n²), the missing cache, and the thing that holds at 1x but melts at 10x, then prioritizes them by how hot the path is and how big the regression. It insists on a number — measure, don't guess — and names the user-facing cost (+300ms p95, OOM under load, timeout at scale).
Use when: reviewing for performance, perf review, investigating latency/slowness, reviewing a hot path, checking caching, capacity/scalability review, reviewing fo…
