In this article, I am going to explain how to create an AWS Lambda function and then call this function from another Lambda function within the same region. This is a useful scenario in which we may need to execute a second lambda function based on the outcome of some previous logic. Another scenario may be to execute a second lambda function several times by using different parameters.

For the sake of this article, we will consider a typical retailer application, in which we can purchase different products from a retailer site using a lambda function.

Figure 1 – Architecture Diagram

If you consider the above architecture diagram, you can see that we have an AWS lambda function – the ParentFunction, which assumes a specific role from the IAM (Invoke Other Lambda Function) and then calls another lambda function – the ChildFunction with a payload. Once the execution of the ChildFunction is completed, it returns a response, which is then passed on to the ParentFunction. The ParentFunction receives the response and handles the job accordingly.

As in this example, let us assume that the ParentFunction is going to call the ChildFunction with a payload of ProductName, Quantity, and the UnitPrice of that product. The ChildFunction, in turn, will process this payload, calculate the total sales amount, generate a transaction reference ID, and return this information to the ParentFunction.

Creating the first AWS Lambda Function – ChildFunction

Let us first go ahead and create the ChildFunction, which will process the input payload and return the results to the ParentFunction.

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