Performance Skills
A curated collection of 8 performance skills for building with AI coding agents.
Bundle Analyzer
Analyze a JS/TS production bundle and surface the biggest size wins — heavy dependencies, duplicate packages, missing code-splitting, oversized polyfills, and dev/server code leaking into the client. Use when a bundle is too large and you need a ranked, actionable reduction plan.
Cold Start Optimizer
Cut cold-start latency for serverless functions and slow-booting apps by measuring the init breakdown, then attacking the dominant phase — artifact size, eager imports, eager connections, or under-provisioned memory — instead of reflexively buying provisioned concurrency. Use when serverless p99 spikes on the first request, when a function times out during init, or when scale-to-zero is hurting user-facing latency.
Flamegraph Analyzer
Turn a CPU profile or flamegraph into a concrete optimization instead of guessing where the time goes: capture under a realistic workload with a sampling profiler, read the graph correctly (width = time, depth ≠ time), find the widest self-time leaves, ask if that work is necessary/redundant/algorithmically wrong, fix the biggest contributor, then re-profile. Use when code is CPU-bound and slow, a function is hot but you don't know which part, or you have a profile you can't interpret.
Load Test Designer
Design a defensible load test — a realistic workload model, a deliberate test type, and SLO-tied pass/fail thresholds — instead of a meaningless tight-loop script that hammers one endpoint. Use when validating capacity or SLOs before a launch or scaling event, when sizing infrastructure, or when an existing load test reports averages that nobody trusts.
Memory Leak Hunter
Find and fix a memory leak in a running app: confirm it's a real leak under steady load, diff two heap snapshots to name the growing object and its retention path, cut the root reference that blocks collection, and re-run to confirm memory plateaus. Use when RSS climbs until OOM/restart, heap grows unbounded across a steady workload, or GC pauses worsen the longer the process runs.
Prompt Cache Optimizer
Restructure an LLM call to maximize prompt-cache hit rate and add response/semantic caching — move the stable prefix (system prompt, instructions, few-shot, context) to the front and variable input to the end, set cache breakpoints, and measure the hit rate and savings. Use when repeated calls share large common context and token cost or latency is too high.
React Render Profiler
Find and fix wasteful React re-renders by classifying the cause — unstable prop/callback/object identities, context value churn, state lifted too high, expensive work in render, or unvirtualized lists — confirming it with a measurement, then applying the one targeted fix and re-measuring. Use when a React UI is janky, slow to type in, or re-renders far more than the data actually changed.
Web Vitals Optimizer
Diagnose and fix Core Web Vitals — LCP, CLS, and INP — by treating real-user field data at p75 as the source of truth, using Lighthouse/WebPageTest only to find the at-fault element, script, or shift, then applying the one targeted fix per metric and re-measuring. Use when a page feels slow, scores poorly on PageSpeed/Lighthouse, or fails CWV in CrUX/RUM field data.