Getting Error while executing lambda through step functions

The following one only answers to this question mentioned above: error : Lambda.Unknown cause: The cause could not be determined because Lambda did not return an error type.

Standard Workflows guarantee exactly one execution of each workflow step, with a maximum duration of one year.

This is from the Step function documentation. It means your step which is invoking your Lambda function has a timeout of almost 1 year. Whereas if you see the Lambda function there's a timeout option.

Now, if your lambda function has a timeout, say for X seconds and the task of the Lambda function takes more than X seconds then your lambda will timeout and won't return any response back to the Step function. This can also generate the above error you mentioned!

But I believe you already know these since it's already been 2 years and 6 months and .... :v :v

You can, but it might not give the results you expect. Especially with your post error handling. However, if you want Lambda to return without waiting for your post response. You can set: context.callbackWaitsForEmptyEventLoop = false