Call DynamoDB APIs with Step Functions

Step Functions can control certain AWS services directly from Amazon States Language (ASL). To learn more, see Working with other services and Pass parameters to a service API.

Note

There is a quota for the maximum input or result data size for a task in Step Functions. This restricts you to 256 KB of data as a UTF-8 encoded string when you send to, or receive data from, another service. See Quotas related to state machine executions.

How the optimized DynamoDB integration is different than the DynamoDB AWS SDK integration

• There is no optimization for the Request Response integration pattern.

• The Wait for a Callback with the Task Token integration pattern is not supported.

• Only GetItem, PutItem, UpdateItem, and DeleteItem API actions are available through optimized integration. Other API actions, such as CreateTable are available using the DynamoDB AWS SDK integration.

Supported Amazon DynamoDB APIs and syntax:

• GetItem

  • Request syntax

  • Supported parameters:

    • Key

    • TableName

    • AttributesToGet

    • ConsistentRead

    • ExpressionAttributeNames

    • ProjectionExpression

    • ReturnConsumedCapacity

  • Response syntax

• PutItem

  • Request syntax

  • Supported parameters:

    • Item

    • TableName

    • ConditionalOperator

    • ConditionExpression

    • Expected

    • ExpressionAttributeNames

    • ExpressionAttributeValues

    • ReturnConsumedCapacity

    • ReturnItemCollectionMetrics

    • ReturnValues

  • Response syntax

• DeleteItem

  • Request syntax

  • Supported parameters:

    • Key

    • TableName

    • ConditionalOperator

    • ConditionExpression

    • Expected

    • ExpressionAttributeNames

    • ExpressionAttributeValues

    • ReturnConsumedCapacity

    • ReturnItemCollectionMetrics

    • ReturnValues

  • Response syntax

• UpdateItem

  • Request syntax

  • Supported parameters:

    • Key

    • TableName

    • AttributeUpdates

    • ConditionalOperator

    • ConditionExpression

    • Expected

    • ExpressionAttributeNames

    • ExpressionAttributeValues

    • ReturnConsumedCapacity

    • ReturnItemCollectionMetrics

    • ReturnValues

    • UpdateExpression

  • Response syntax

Parameters in Step Functions are expressed in PascalCase

Even if the native service API is in camelCase, for example the API action startSyncExecution, you specify parameters in PascalCase, such as: StateMachineArn.

The following is a Task state that retrieves a message from DynamoDB.

    "Read Next Message from DynamoDB": {
      "Type": "Task",
      "Resource": "arn:aws:states:::dynamodb:getItem",
      "Parameters": {
        "TableName": "TransferDataRecords-DDBTable-3I41R5L5EAGT",
        "Key": {
          "MessageId": {"S.$": "$.List[0]"}
        }
      },
      "ResultPath": "$.DynamoDB",
      "Next": "Send Message to SQS"
    },
        

To see this state in a working example, see the Transfer data records (Lambda, DynamoDB, Amazon SQS) sample project.

For information about how to configure IAM permissions when using Step Functions with other AWS services, see IAM Policies for integrated services.