performance

/performance — Performance Analysis & Optimization

Profile application performance, identify bottlenecks, and implement optimizations with before/after benchmarks.

Instructions

Step 1: Define Performance Scope

From $ARGUMENTS:

• Build performance — Compilation, bundling speed
• Runtime performance — API response times, rendering speed
• Database performance — Query execution, indexing
• Memory performance — Leaks, allocation patterns
• Bundle size — JavaScript/CSS output size

Step 2: Baseline Measurement

ALWAYS measure BEFORE optimizing:

# Build metrics
time npm run build 2>&1

# Bundle analysis (if applicable)
npx next build --profile 2>&1 || npx vite build --report 2>&1

# Bundle size
find dist -name "*.js" -exec wc -c {} + 2>/dev/null | sort -rn | head -10

# Runtime profiling (Node.js)
node --prof [entry-point] 2>/dev/null

# Database queries (if applicable)
# Check for slow queries in logs

Record baseline:

## Baseline Measurements
| Metric | Value | Target |
|--------|-------|--------|
| Build time | [Xs] | [Xs] |
| Bundle size | [XKB] | [XKB] |
| API response (p50) | [Xms] | [Xms] |
| API response (p99) | [Xms] | [Xms] |
| Memory usage | [XMB] | [XMB] |

Step 3: Identify Bottlenecks

Analyze for common performance issues:

# Large files (potential bundle bloat)
find src -name "*.ts" -o -name "*.tsx" | xargs wc -l | sort -rn | head -20

# Heavy imports
grep -rn "import.*from" --include="*.ts" --include="*.tsx" . | grep -v node_modules | sort -t: -k3 | head -30

# N+1 query patterns
grep -rn "await.*find\|await.*query\|\.map.*async" --include="*.ts" . | grep -v node_modules | head -20

# Missing indexes (check schema)
grep -rn "where\|WHERE\|findBy\|findOne" --include="*.ts" --include="*.sql" . | grep -v node_modules | head -20

# Synchronous operations in async context
grep -rn "readFileSync\|writeFileSync\|execSync" --include="*.ts" --include="*.js" . | grep -v node_modules | head -10