Database Connection Pooling: Why Your API Is Slow Under Load

Every database query needs a connection. Opening a new TCP connection + SSL handshake + auth for every request takes 20-50ms. Connection pooling keeps connections open and reuses them.

How Pooling Works

import { Pool } from "pg";

const pool = new Pool({
  host: process.env.DB_HOST,
  port: 5432,
  database: process.env.DB_NAME,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  max: 20,                 // max connections in pool
  idleTimeoutMillis: 30000, // close idle connections after 30s
  connectionTimeoutMillis: 2000, // fail if cannot connect in 2s
});

pool.on("error", (err) => {
  console.error("Unexpected idle client error", err);
});