When requests to Step Function fail, Workflow Service performs exponential backoff retries to notify Step Function service. Number of retries = 3 The total duration of all attempts doesn't exceed 10 seconds, the processing must not exceed the message visibility timeout.

public void send(String message) throws InterruptedException {
    int count = 0;
    while (count < 3) {
        try {
            sqs.sendMessage(queueUrl, message);
            break;
        } catch (AmazonServiceException ex) {
            count++;
            
            if (ex.getErrorCode().equals("RequestError") && ex.getStatusCode() == 400) {
                System.out.println("SQS message payload size too large, will retry with a smaller message size");
                sqs.sendMessage(queueUrl, message.substring(0, Math.min(message.length(), 256)));
            }
        }
        
        Thread.sleep(Math.min((int) Math.pow(2, count) * 1000, 10000));
    }
}