RCT.07.03 Mid-level

proxy.ts, route handlers and deployment

Comes up in: React, Frontend system design

This concept is being written. It gets the full five steps — explanation, predict, interview angle, practice with tests, and review cards. Here is exactly what it will cover, so you can study it elsewhere in the meantime.

What it covers

proxy.ts replaces middleware.ts (Next 16, Node runtime
middleware.ts is deprecated but still works for Edge)
route handlers
environment variables (server vs NEXT_PUBLIC_)
image and font optimisation
Turbopack default
deploying to Vercel vs other hosts (adapters, OpenNext for Cloudflare)

Words you will know

proxyroute handlerTurbopackadapter

What you will practise

auth redirect in proxy.ts

Interview questions this answers

What replaced middleware.ts in Next.js 16 and why?