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Vercel

Tested with: Vercel CLI 39 · Next.js 15 · @vercel/functions 1.5 · PostgreSQL 17

  1. Add the connection string as an environment variable. Use the pooled endpoint for serverless functions (-pool host, see Connection pooling) and the direct endpoint for prisma migrate in CI.

    shell
    vercel env add DATABASE_URL production
    # postgresql://app:<password>@pg-7f3k-pool.us-east.databasezy.com:5432/app?sslmode=verify-full
    vercel env add DIRECT_URL production
    # postgresql://app:<password>@pg-7f3k.us-east.databasezy.com:5432/app?sslmode=verify-full

    Node drivers on Vercel use the OS trust store, so no CA file is needed; sslmode=verify-full still verifies the hostname.

  2. Allow Vercel’s egress. Functions have no fixed IP by default; enable Secure Compute (Enterprise) for static IPs, or allow all and rely on TLS plus credentials, which the portal flags.

    shell
    zb api PUT /v1/orgs/{org}/instances/pg-7f3k/network -d '{"allow_cidrs": ["0.0.0.0/0", "::/0"]}'   # everyone; flagged in the portal

  3. Connect with a small pool per function instance.

    lib/db.ts
    import { Pool } from "pg";
    

    const globalForPg = globalThis as unknown as { pool?: Pool };
    export const pool =
      globalForPg.pool ?? new Pool({ connectionString: process.env.DATABASE_URL, max: 3, ssl: true });
    if (process.env.NODE_ENV !== "production") globalForPg.pool = pool;

Edge runtime

Section titled “Edge runtime”

The Edge runtime has no TCP sockets. Use libSQL (HTTP) directly, or PostgreSQL through an HTTP-capable driver such as @neondatabase/serverless-style fetch drivers pointed at a Node function, or simply run the route on the Node runtime (export const runtime = "nodejs"). Valkey has no HTTP interface; keep cache access in Node functions.

Preview deployments

Section titled “Preview deployments”

Create one instance per preview branch from a GitHub Action (see Argo CD and Helm patterns for the CLI steps) and set DATABASE_URL on the preview environment with vercel env add DATABASE_URL preview <branch>.