TL;DR
We're going to build a "user uploads a video, user watches the video" feature in a Next.js 15 app. The browser uploads directly to a managed video API so our server never holds bytes, a webhook flips the row from processing to ready, and the watch page plays an HLS manifest. ~120 lines across four files.
We'll use FastPix as the managed API in this tutorial because the encoding is free on the standard plan and the $25 signup credit covers the bytes you'll burn while iterating. The same shape works against Mux, api.video, or Cloudflare Stream. Only the endpoint names and webhook field names change.
What we're building
POST /api/uploads returns a one-shot direct-upload URL.
