My AI-Built App Is Slow — 8 Performance Fixes That Actually Work

AI tools optimise for correct, readable code — not necessarily performant code. The patterns that make AI-generated code easy to understand are often the same patterns that make it slow at scale. Here are the 8 highest-impact performance fixes for AI-built apps.

Fix 1: Add Database Indexes

This is the single highest-impact fix for most slow apps. If your queries filter by user_id, status, or created_at and those columns have no indexes, every query does a full table scan. Add an index on every column you filter or sort by. In Supabase: Database → Indexes → New Index.

Fix 2: Implement Pagination

Loading all rows from a table is fast with 50 rows and unusable with 5,000. Add LIMIT and OFFSET to every list query and show 20 to 50 items per page with a Load More button. This single change can make a slow app feel instant.

Fix 3: Stop Fetching on Every Render

useEffect with missing or wrong dependencies causes the same data to be fetched repeatedly on every state update and navigation event. Fix: Add correct dependencies to useEffect and consider SWR or React Query for smart caching.

Fix 4: Optimise Images

Unoptimised images are the most common cause of slow page loads. A single 3MB hero image makes your page feel broken on a mobile connection. Compress all images to under 200KB. For user uploads, use Supabase Storage's image transformation API to serve correctly sized versions.

Fix 5: Lazy Load Heavy Components

Large chart libraries, rich text editors, and maps loaded on the initial page load slow everything down even for users who never use those features. Use React.lazy() and Suspense to only load these when actually needed.

Fix 6: Select Only the Columns You Need

Replace select('*') with select('id, name, status') — fetching only the columns your UI actually displays. This reduces the data transferred on every query.

Fix 7: Move Filtering to the Database

If your app fetches a large dataset and then filters it in JavaScript, move that filtering to the SQL query instead. SQL is orders of magnitude faster at filtering and aggregating data than JavaScript running in a browser.

Fix 8: Add a CDN

If your app's static files are served from a single server region, users far from that region experience slow loads. Deploying to Vercel or Netlify automatically puts static assets on a CDN. If you are on a VPS, add Cloudflare in front of it — it is free and makes an immediate difference.

Most AI-built apps have at least 3 of these issues. Applying all 8 typically improves load time by 50 to 80 percent. If the app is still slow after these fixes, the issue is in specific query or component architecture and needs a developer to profile and diagnose.