Add more than one data source

Data API builder supports hybrid endpoints through the use of data source files, allowing you to define multiple data sources and their entities in separate configuration files.

This is useful when:

• You need to expose entities from more than one database
• You want to organize configurations modularly
• You need to manage different data backends independently

Structure

To define multiple data sources, create multiple configuration files and reference them in the data-source-files array of the top-level config.

Top-level file

{
  "data-source-files": [
    "dab-config-sql.json",
    "dab-config-cosmos.json"
  ],
  "runtime": {
    "rest": {
      "enabled": true
    }
  }
}

Child file: dab-config-sql.json

{
  "data-source": {
    "database-type": "mssql",
    "connection-string": "@env('SQL_CONNECTION_STRING')"
  },
  "entities": {
    "Book": {
      "source": {
        "object": "dbo.Books"
      },
      "permissions": [
        { "role": "anonymous", "actions": [ "read" ] }
      ]
    }
  }
}

Child file: dab-config-cosmos.json

{
  "data-source": {
    "database-type": "cosmosdb_nosql",
    "connection-string": "@env('COSMOS_CONNECTION_STRING')",
    "database-name": "library"
  },
  "entities": {
    "LoanRecord": {
      "source": {
        "object": "LoanRecords"
      },
      "permissions": [
        { "role": "anonymous", "actions": [ "read" ] }
      ]
    }
  }
}

Behavior

• Only the top-level file's runtime settings are respected
• Every child file must contain both a data-source and entities section
• Entity names must be globally unique across all files
• Entities defined in separate files cannot reference each other via relationships
• Files can be nested in subfolders as needed

Benefits

• Clean separation of configuration per backend
• Enables scalable multi-database APIs
• Simplifies maintenance for complex systems

Limitations

• No relationships across configuration files
• Circular file references are not allowed
• Only the top-level file controls runtime behavior