Step Function - dynamodb query with Boolean Filter


Using Step function AWS SDK integration for querying dynamodb table with key condition and filter condition, below is the query works fine outside of step-function. When trying to save the state machine after adding this, get the below Error.

Ddb Query

  "TableName": "test",
  "ScanIndexForward": true,
  "KeyConditionExpression": "pk = :pk",
  "FilterExpression":"scheduled = :scheduled",
  "ExpressionAttributeValues": {
    ":pk": {
      "S": "test"
    ":scheduled": {

** Error Saving State Machine **

There are Amazon States Language errors in your state machine definition. Fix the errors to continue.

    The field "BOOL" is not supported by Step Functions

For more information, see Amazon States Language
3 Answers
Accepted Answer

The optimized service integrations accept BOOL, however there is a difference between how AWS SDK integrations handle request parameters. If you switch from "BOOL" to "Bool" it will work. All parameters for AWS SDK integrations must be in PascalCase.


The API action will always be camel case, and parameter names will be Pascal case. For example, you could use Step Functions' startSyncExecution API action and specify the parameter StateMachineArn.

answered 2 years ago

According to this, you should change ":scheduled": { "BOOL":true } to ":scheduled": true Did not try it.

profile pictureAWS
answered 2 years ago
  • Thanks for your suggestion. But unfortunately this doesn't work as its javascript. Looks like internally the step-function uses JAVA SDK. Was able to figure this out from the error:

    There are Amazon States Language errors in your state machine definition. Fix the errors to continue.
    Cannot construct instance of `$BuilderImpl` (although at least one Creator exists): no boolean/Boolean-argument constructor/factory method to deserialize from boolean value (true)
    For more information, see

    Here is the Java doc for Filter Expression. Its like chicken and egg situation here:

    1. Java sdk for dynamodb accepts only a map of <String, AttributeValue> ({"pk":{"S":"data"}, "scheduled":{"BOOL":true}}
    2. in State Language "BOOL" is a reserved keyword probably and not being accepted

Querying is not supported in SFN, just get, put, delete, and update.

answered 2 years ago
  • Query is supported by StepFunctions.

  • oops i was looking at optimized integrations. sorry!

You are not logged in. Log in to post an answer.

A good answer clearly answers the question and provides constructive feedback and encourages professional growth in the question asker.

Guidelines for Answering Questions