How do you handle 404 errors in Express?

Short answer: You define a catch-all middleware after all routes: app.use((req, res) => { res.status(404).json({ message: 'Route not found' }); });

Example code

You define a catch-all middleware after all routes: app.use((req, res) => { res.status(404).json({ message: 'Route not found' }); });

Real-world example (ShopNest)

Express middleware authenticates JWT, then the /orders route handler creates the order.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.