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node-postgres ​

node-postgres (pg) is the most widely used PostgreSQL client for Node.js.

Read-only transactions ​

node-postgres doesn't have built-in read-only transaction support. Use raw SQL instead:

db.js
javascript
await client.query("BEGIN READ ONLY");
const result = await client.query("SELECT ...");
await client.query("COMMIT");

Halephant detects BEGIN READ ONLY and routes the transaction to a replica.

Separate pools ​

If you handle routing at the application level, create two pools with different users:

db.js
javascript
const { Pool } = require("pg");

const writePool = new Pool({
    host: "halephant",
    port: 6432,
    database: "myapp",
    user: "myapp",
    ssl: false,
});

const readPool = new Pool({
    host: "halephant",
    port: 6432,
    database: "myapp",
    user: "myapp_ro",
    ssl: false,
});

See the read replica guide for halephant configuration.