Connecting from Node.js with a Connection Pool

Applications typically use a connection pool to reuse database connections rather than creating a new connection for every query. Pool size should be considered across all application instances, not just one process: several replicas each configured with a large pool can exhaust the database's connection limit. Set timeouts, handle errors, and release checked-out clients reliably.

Keep database credentials in environment configuration or a secret manager. A connection pool manages connectivity, not authorization; the database role still needs appropriately scoped privileges.

Use node-postgres safely

import pg from "pg";

const pool = new pg.Pool({
  connectionString: process.env.DATABASE_URL,
  max: 10,
  idleTimeoutMillis: 30_000,
  connectionTimeoutMillis: 5_000
});

const result = await pool.query(
  "SELECT id, name FROM customers WHERE id = $1",
  [customerId]
);

💡 This example uses the pg package. Choose a pool size based on total application replicas and database capacity, and ensure the application closes the pool during graceful shutdown.

Key Takeaways

Use a pool for typical server applications.
Calculate total connections across all replicas.
Use bound parameters and graceful shutdown handling.

Knowledge Check

Why can a pool size of 20 per process be dangerous with many replicas?

Connecting from Node.js with a Connection Pool

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