Edge Config & KV Storage

12. Edge Config & KV Storage

12.1 Edge Config

A globally replicated key-value store designed for ultra-low latency reads at the edge. Data is replicated to every PoP.

import { get } from '@vercel/edge-config';

// In Middleware (Edge Runtime) — near-zero latency
export async function middleware(request) {
  const maintenanceMode = await get('maintenance-mode');
  if (maintenanceMode) {
    return NextResponse.redirect('/maintenance');
  }
}

Use cases:

• Feature flags
• Maintenance mode toggle
• A/B test configuration
• Allowed/blocked IP lists
• Rate limiting configuration

Critical limitation: Write propagation is eventually consistent with seconds of latency. Edge Config is for read-heavy data that changes infrequently. Do not use it for user sessions or real-time data.

12.2 Vercel KV (Redis-compatible)

For general-purpose key-value storage in Serverless Functions:

import { kv } from '@vercel/kv';

// Rate limiting
const requests = await kv.incr(`rate:${userId}`);
await kv.expire(`rate:${userId}`, 60);  // reset after 60 seconds
if (requests > 100) return new Response('Too Many Requests', { status: 429 });

12.3 Vercel Blob

Object storage for files — images, videos, documents:

import { put } from '@vercel/blob';

export async function POST(request) {
  const form = await request.formData();
  const file = form.get('file');
  const blob = await put(file.name, file, { access: 'public' });
  return Response.json({ url: blob.url });
}

12.4 Vercel Postgres

Managed PostgreSQL (powered by Neon serverless Postgres):

import { sql } from '@vercel/postgres';

const { rows } = await sql`SELECT * FROM users WHERE id = ${userId}`;