Node.js client (alpha)

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SDK Features

• Real-time streaming of database changes: Changes made by one user are instantly streamed to all other users with access to that data. This keeps clients automatically in sync without manual polling or refresh logic.
• Direct access to a local SQLite database: Data is stored locally, so apps can read and write instantly without network calls. This enables offline support and faster user interactions.
• Asynchronous background execution: The SDK performs database operations in the background to avoid blocking the application’s main thread. This means that apps stay responsive, even during heavy data activity.
• Query subscriptions for live updates: The SDK supports query subscriptions that automatically push real-time updates to client applications as data changes, keeping your UI reactive and up to date.
• Automatic schema management: PowerSync syncs schemaless data and applies a client-defined schema using SQLite views. This architecture means that PowerSync SDKs can handle schema changes gracefully without requiring explicit migrations on the client-side.

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Quickstart

Add the PowerSync Node NPM package to your project:

npm install @powersync/node

npm install @powersync/node

yarn add @powersync/node

pnpm install @powersync/node

Required peer dependencies

This SDK requires @powersync/better-sqlite3 as a peer dependency:

npm install @powersync/better-sqlite3

npm install @powersync/better-sqlite3

yarn add @powersync/better-sqlite3

pnpm install @powersync/better-sqlite3

Common installation issues

The @powersync/better-sqlite package requires native compilation, which depends on certain system tools. This compilation process is handled by node-gyp and may fail if required dependencies are missing or misconfigured.

Refer to the PowerSync Node package README for more details.

Next, make sure that you have:

• Signed up for a PowerSync Cloud account (here) or self-host PowerSync.
• Configured your backend database and connected it to your PowerSync instance.

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1. Define the schema

The first step is defining the schema for the local SQLite database.

This schema represents a “view” of the downloaded data. No migrations are required — the schema is applied directly when the local PowerSync database is constructed (as we’ll show in the next step). You can use this example as a reference when defining your schema.

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2. Instantiate the PowerSync Database

Next, you need to instantiate the PowerSync database — this is the core managed database.

Its primary functions are to record all changes in the local database, whether online or offline. In addition, it automatically uploads changes to your app backend when connected.

Example:

import { PowerSyncDatabase } from '@powersync/node';
import { Connector } from './Connector';
import { AppSchema } from './Schema';

export const db = new PowerSyncDatabase({
  // The schema you defined in the previous step
  schema: AppSchema,
  database: {
    // Filename for the SQLite database — it's important to only instantiate one instance per file.
    dbFilename: 'powersync.db',
    // Optional. Directory where the database file is located.'
    // dbLocation: 'path/to/directory'
  },
});

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3. Integrate with your Backend

The PowerSync backend connector provides the connection between your application backend and the PowerSync client-slide managed SQLite database.

It is used to:

1. Retrieve an auth token to connect to the PowerSync instance.
2. Apply local changes on your backend application server (and from there, to your backend database)

Accordingly, the connector must implement two methods:

1. PowerSyncBackendConnector.fetchCredentials - This is called every couple of minutes and is used to obtain credentials for your app backend API. -> See Authentication Setup for instructions on how the credentials should be generated.
2. PowerSyncBackendConnector.uploadData - Use this to upload client-side changes to your app backend. -> See Writing Client Changes for considerations on the app backend implementation.

Example:

import { UpdateType } from '@powersync/node';

export class Connector implements PowerSyncBackendConnector {
    constructor() {
        // Setup a connection to your server for uploads
        this.serverConnectionClient = TODO;
    }

    async fetchCredentials() {
        // Implement fetchCredentials to obtain a JWT from your authentication service.
        // See https://docs.powersync.com/installation/authentication-setup
        // If you're using Supabase or Firebase, you can re-use the JWT from those clients, see
        // - https://docs.powersync.com/installation/authentication-setup/supabase-auth
        // - https://docs.powersync.com/installation/authentication-setup/firebase-auth
        return {
            endpoint: '[Your PowerSync instance URL or self-hosted endpoint]',
            // Use a development token (see Authentication Setup https://docs.powersync.com/installation/authentication-setup/development-tokens) to get up and running quickly
            token: 'An authentication token'
        };
    }

    async uploadData(database) {
      // Implement uploadData to send local changes to your backend service.
      // You can omit this method if you only want to sync data from the database to the client

      // See example implementation here: https://docs.powersync.com/client-sdk-references/javascript-web#3-integrate-with-your-backend
    }
}

With your database instantiated and your connector ready, call connect to start the synchronization process:

await db.connect(new Connector());
await db.waitForFirstSync(); // Optional, to wait for a complete snapshot of data to be available

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Usage

After connecting the client database, it is ready to be used. The API to run queries and updates is identical to our web SDK:

// Use db.get() to fetch a single row:
console.log(await db.get('SELECT powersync_rs_version();'));

// Or db.getAll() to fetch all:
console.log(await db.getAll('SELECT * FROM lists;'));

// Use db.watch() to watch queries for changes:
const watchLists = async () => {
  for await (const rows of db.watch('SELECT * FROM lists;')) {
    console.log('Has todo lists', rows.rows!._array);
  }
};
watchLists();

// And db.execute for inserts, updates and deletes:
await db.execute(
  "INSERT INTO lists (id, created_at, name, owner_id) VALUEs (uuid(), datetime('now'), ?, uuid());",
  ['My new list']
);

PowerSync runs queries asynchronously on a background pool of workers and automatically configures WAL to allow a writer and multiple readers to operate in parallel.

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Configure Logging

import { createBaseLogger, LogLevel } from '@powersync/node';

const logger = createBaseLogger();

// Configure the logger to use the default console output
logger.useDefaults();

// Set the minimum log level to DEBUG to see all log messages
// Available levels: DEBUG, INFO, WARN, ERROR, TRACE, OFF
logger.setLevel(LogLevel.DEBUG);