Some data needs to be read on every request but changes rarely — feature flags, kill switches, maintenance mode toggles, allowed IP lists, A/B test configs. The typical approach is to:

• Store it in a database and add latency to every request
• Hard-code it in environment variables and redeploy every change
• Use Redis/Upstash which still adds a network round-trip

None of these are ideal when you need a change to take effect globally in under a second with near-zero read latency.

Edge Config is a global, ultra-low-latency key-value data store. Reads happen in under 1ms because the data is stored at the edge — co-located with your serverless functions and edge middleware. Updates propagate globally in seconds. It's designed specifically for configuration data that's read often but written rarely.

Read a value

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

export async function middleware(request: NextRequest) {
  const isMaintenanceMode = await get("maintenance_mode");

  if (isMaintenanceMode) {
    return NextResponse.rewrite(new URL("/maintenance", request.url));
  }

  return NextResponse.next();
}

Feature flag check in a route handler

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

export async function GET() {
  const newCheckoutEnabled = await get<boolean>("new_checkout");

  return Response.json({ feature: newCheckoutEnabled ?? false });
}

Read multiple values at once

import { getAll } from "@vercel/edge-config";

const config = await getAll(["feature_x", "feature_y", "rate_limit"]);
// { feature_x: true, feature_y: false, rate_limit: 100 }

Check if a key exists

import { has } from "@vercel/edge-config";

const exists = await has("beta_users_list");