Cloudflare Pages edge runtime is fast. It's also not Node.js. These two facts will ruin your night if you treat them as the same thing.

How I Got Here

I was building WealthifyX a Next.js financial calculators suite with Upstash Redis for email subscriptions. I picked Cloudflare Pages because it's fast, cheap, and global. Reasonable call.

Then the Redis client started failing. No clear error, just silent failure on the email subscribe endpoint.

What Was Actually Happening

After a few hours of debugging, I found it: Cloudflare Pages runs code in a V8 isolate, not a Node.js process. That isolate strips out Node.js globals Buffer, certain crypto APIs, gone. The Upstash Redis client depended on them.

I had assumed "edge runtime" meant "Node.js, but faster and closer to the user." It doesn't. It's a different environment with a different set of available APIs. The Cloudflare docs say this, but I hadn't read closely enough before committing to the deployment target.

The Fix

I moved to Vercel. For routes that worked fine in the edge runtime, nothing changed. For the Redis-dependent routes, I added export const runtime = 'nodejs' to explicitly opt into the Node.js runtime.

// api/subscribe/route.ts
export const runtime = 'nodejs'

export async function POST(req: Request) {
  // Upstash Redis client works fine here
}

Migration took a few hours. Zero downtime, zero data loss.

What I'd Do Differently

Check whether your third-party clients support edge runtimes before picking a host. Most client libraries have a section in their docs about this. Upstash does, I just didn't check it first.

Edge runtimes are worth using. But they're not Node.js, and assuming they are is how you end up migrating at 2am.