Vercel KV Primer

What is Vercel KV?

Vercel KV is a durable Redis-compatible database built on Upstash. It operates over HTTP, which means no persistent TCP connections and no connection pooling headaches inside serverless functions. Reads and writes complete in single-digit milliseconds from edge regions.

Why Meridian chose it

• @upstash/redis client initializes in ~2ms with an HTTP REST token — no handshake delay.
• Atomic INCR andEXPIRE give us leaky-bucket rate limiters without external state.
• Per-route feature flags stored as simple string keys let us ship dark without redeploying.

Pattern: session cache

Meridian validates license keys on every cold start. We cache the result in KV with a 60-second TTL so repeated requests from the same edge region hit memory instead of the licensing backend.

// pages/api/verify.ts
import { Redis } from '@upstash/redis';

const kv = Redis.fromEnv();

export default async function handler(req) {
  const key = req.headers['x-license-key'];
  const cached = await kv.get(`license:${key}`);
  if (cached) return res.status(200).json(cached);

  const result = await verifyAgainstKeyAuth(key);
  await kv.set(`license:${key}`, result, { ex: 60 });
  return res.status(200).json(result);
}

Pitfalls

• KV is eventually consistent across regions — do not use it for strongly-ordered counters.
• Maximum value size is 1 MB. Store large blobs in Vercel Blob and keep the URL in KV.
• Every command is a round-trip. Batch withpipeline() when you need multiple reads.