Perf Check

Performance Check

Analyze and report on project performance metrics.

Arguments

• /perf-check — full analysis
• /perf-check --bundle — bundle size only
• /perf-check --lighthouse <url> — Lighthouse audit
• /perf-check --deps — dependency weight analysis
• /perf-check --code — code-level pattern check

Workflow

Phase 1: Detect Scope

• Frontend: bundle size, lighthouse, dependency weight
• Backend: startup time, memory, dependency weight
• Fullstack: both

Phase 2: Bundle Analysis

• Build and measure output: du -sh dist/ build/ .next/
• Check largest dependencies: npx -y cost-of-modules
• Identify tree-shaking opportunities

Phase 3: Lighthouse (if URL available)

npx -y lighthouse <url> --output json --chrome-flags="--headless --no-sandbox"

Phase 4: Dependency Analysis

Flag heavy dependencies:

• moment → dayjs or date-fns
• lodash (full) → lodash-es or individual imports
• aws-sdk v2 → @aws-sdk/client-* v3

Phase 5: Code Anti-patterns

• N+1 queries (loop with await)
• JSON.parse(JSON.stringify()) for clone
• Missing useMemo/useCallback on expensive operations
• Sync file ops in request handlers
• Missing database indexes

Phase 6: Report

# Performance Report

## Bundle
- Total: 1.2MB (gzipped: 380KB)

## Issues Found
🔴 moment.js adds 230KB — replace with dayjs (2KB)
🟡 Full lodash import — use lodash-es

## Recommendations (by impact)
1. Replace moment → dayjs (saves ~228KB)
2. Code-split vendor chunk

Rules

• Don't make changes — only analyze and report
• Sort recommendations by estimated impact
• Include specific numbers (KB saved, ms improved)
• Suggest alternatives for every heavy dependency flagged