Optimizing Replit Agent-Generated Code for Performance

Cold start latency (5-15 seconds) on Replit hosting. Database queries without indexes. No caching layer. Synchronous processing for operations that should be async. Large response payloads without pagination or compression

Migrate to always-on hosting to eliminate cold starts. Add database indexes for common queries. Implement Redis or in-memory caching for frequently accessed data. Make long-running operations async with job queues. Add response compression and pagination

Before optimizing, measure. Use your browser's Lighthouse audit to get a baseline score. Check Core Web Vitals (LCP, FID, CLS) — these directly affect your Google ranking. Use the Performance tab in DevTools to identify which components take the longest to render. For server-side performance, add timing logs to API routes to find slow endpoints.

The fastest way to improve performance: optimize and lazy-load images, enable compression on your server, remove unused CSS and JavaScript, implement code splitting so users only download code for the page they're viewing, and add proper caching headers for static assets. These changes alone can cut load times significantly.

If your Replit Agent app uses a database, slow queries are often the biggest performance bottleneck. Add indexes on columns you filter or sort by. Use SELECT to fetch only the columns you need instead of SELECT *. Implement pagination for lists — loading 10,000 rows at once will always be slow. Consider adding a caching layer for data that doesn't change frequently.