performance-review

Performance Review

When reviewing code for performance issues, check each category below. Reference the detailed checklist in references/performance-checklist.md.

Database & Queries

• N+1 query patterns (queries inside loops)
• Missing database indexes for frequently queried fields
• Unbounded queries without LIMIT/pagination
• SELECT * instead of selecting only needed columns
• Missing connection pooling

Memory & Resources

• Memory leaks: event listeners not removed, intervals not cleared, growing caches without bounds
• Large objects held in memory unnecessarily
• Unbounded arrays or maps that grow with usage
• Missing cleanup in component unmount/destroy lifecycle

Rendering (Frontend)

• Unnecessary re-renders (missing React.memo, useMemo, useCallback where appropriate)
• Large component trees re-rendering for small state changes
• Missing virtualization for long lists
• Synchronous heavy computation blocking the main thread
• Large bundle sizes from unnecessary imports

API & Network

• Missing caching for frequently accessed, rarely changing data
• Sequential API calls that could be parallelized
• Missing pagination for large data sets
• Over-fetching data (requesting more than needed)
• Missing request deduplication

Algorithmic Complexity

• O(n²) or worse operations on potentially large datasets
• Repeated computation that could be memoized
• String concatenation in loops (use array join or template literals)
• Unnecessary sorting or filtering passes

Severity Levels

• 🔴 CRITICAL: Will cause performance degradation under normal load
• 🟠 HIGH: Will cause issues at scale
• 🟡 MEDIUM: Optimization opportunity with measurable impact
• 🔵 LOW: Minor optimization suggestion