S3 object and lambda function in step machine with the asynchronous express workflows

Question

My state machine starts with a `MAP` state. Inside the `Map` state,  there are 2 tasks, one after one (task#1 invokes lambda A, task#2 invokes lambda B). The lambda A will process the files conversion, upload those files into S3, and return a S3 object key.  The lambda B will grab the S3 object key from task#1, get the object from S3, and then interact with the third party API.

My question is that before the lambda B is invoked, is there a way to notify the state machine that the files have been saved in S3 and ready to be read? Could we implement the [S3-EventBridge](https://docs.aws.amazon.com/AmazonS3/latest/userguide/EventBridge.html) in the asynchronous express workflows?

Accepted Answer

Why do you need to notify the state machine about it? Lambda A writes the file and only returns when the file is on S3. Lambda B will not be invoked until Lambda A finishes (assuming they are in sequence and not in a Parallel state).

S3 object and lambda function in step machine with the asynchronous express workflows

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