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The options below apply when self-hosting the PowerSync Service with a SQL Server source database. Cloud-hosted PowerSync instances do currently not expose these settings.

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Connect to Azure SQL Database using a Service Principal

As an alternative to using standard SQL Login via username and password, PowerSync can connect to your Azure SQL Database using a Service Principal. Update your config.yaml file to use the Service Principal for authentication:
config.yaml
# Settings for source database replication
replication:
  connections:
    - type: mssql
      database: <YOUR_DATABASE_NAME>
      schema: <YOUR_SCHEMA_NAME> # Optional, defaults to dbo
      hostname: <YOUR_HOSTNAME>
      port: 1433 # Default port for SQL Server

      authentication:
        type: azure-active-directory-service-principal-secret
        options:
          clientId: <YOUR_CLIENT_ID>
          tenantId: <YOUR_TENANT_ID>
          clientSecret: <YOUR_CLIENT_SECRET>

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Create a New App Registration

  1. Go to the Azure portal and navigate to App registrations >.
  2. Click New registration.
  3. Fill in the required fields:
    • Name: Give your app user a name, e.g. “powersync_user”.
    • Redirect URI: Leave this blank.
    • Supported account types: Select Accounts in this organizational directory only.
  4. Click Register.
  5. Copy the Application (Client) ID and Directory (Tenant) ID.

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Create a Client Secret

  1. Navigate to the app registration you created in the previous step.
  2. In the left navigation menu, under Manage, click Certificates & secrets.
  3. Click New client secret.
  4. Fill in the required fields:
    • Description: Enter a description for the secret
    • Expires: Select an expiration date
  5. Click Add.
  6. Important: Copy the Value - this is the client secret and will not be shown again.

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Configure the Database User

  1. Connect to the SQL Server database using an account with administrative privileges.
  2. Create a new user linked to the app registration:
CREATE USER [powersync_user] FROM EXTERNAL PROVIDER;
  1. Complete the rest of the user setup by following the instructions in Source Database Setup.

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Additional Configuration Options

The below configuration options can be set in the additionalConfig section under the connections section of the config.yaml file.
All of these configuration options are optional and can be omitted if the default values are acceptable.
pollingIntervalMs: The polling interval is the frequency at which the PowerSync SQL Server Adapter polls the SQL Server Change tables for changes. Lowering this value helps reduce latency in the replication process, but also increases the load on the SQL Server database and the PowerSync Service. pollingBatchSize The polling batch size is the number of transactions that the PowerSync SQL Server Adapter will process in each polling cycle. Increasing this value can increase throughput at the cost of increased memory usage. If the volume of transactions being replicated is high, and memory is available, it is recommended to increase this value. trustServerCertificate: Whether to trust the server certificate. Set to true for local development and self-signed certificates. Set to false when connecting to Azure SQL Database.
config.yaml
connections:
  - type: mssql
    additionalConfig:
      pollingIntervalMs: 1000 # Default is 1000ms
      pollingBatchSize: 10 # Default is 10
      trustServerCertificate: false # Default is false