How to send response from AWS lambda to client and continue processing code

I am running a piece of Python code on AWS Lambda. I am triggering the code through Postman. The lambda script once triggered can run for around 5mins. So the client has to wait for a response for that time. Instead I want my lambda script to read the request body, process the response body and send the response and still keep running the remaining part of the script.

How do I achieve this? How is this use case achieved usually in a server based application?

I thought of having the remaining part of the code as another Lambda function and triggering it from this function using the requests library. Once triggered I thought of sending the response to the client but the even if I trigger another function it is still going to wait for a response.

You can invoke the second Lambda function Event Invocation Type, which will allow your first function to return a response to your client while the other runs in the background.

Alternatively, you might benefit from using AWS Step Functions for the asynchronous part, as you can make it more resilient and observable.

And if you are looking to do something richer here, this is an interesting blog post to show how you can pair asynchronous server side processing with visibility to the client side.

https://aws.amazon.com/blogs/compute/implementing-reactive-progress-tracking-for-aws-step-functions/