AWS Tutorial: Fixing None Return Type in Durable Lambda Calls

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If you’re working with AWS Lambda and want to improve how you invoke child functions, skipping the context.invoke() method and instead using a durable step with boto3 can make your process simpler and more reliable. This approach ensures your Lambda functions handle JSON payloads smoothly and keeps your code easy to understand.

Here’s a straightforward way to set this up:

Start by importing the necessary modules. You’ll need to bring in boto3 for AWS interactions and your durable execution SDK to handle checkpointing and retries.

Create a function decorated with @durable_step. Inside this function, initialize the Lambda client using boto3.client('lambda'). Use this client to invoke your target Lambda, passing the function’s ARN and the payload as a JSON string.

The response from Lambda will come back as a stream, so read and parse it with json.loads(). This result will be returned from your function.

Then, in your main handler, use @durable_execution to wrap your code. Call the context.step() method with your durable step function. You can pause with context.wait() if needed, and everything will be tracked for retries or checkpoints.

Your child Lambda function doesn’t have to change at all. It will receive a normal JSON object—like {"order_id": 1234}—and process it as usual.

This setup ensures your Lambda functions are easy to maintain and debug. Since responses are plain JSON, you avoid any complex wrapping or custom formats. Plus, using this method with durable steps gives your application resilience, especially in cases of retries or failures.

If this method works for you, marking it as the accepted solution helps others find effective guidance. If any part is unclear or you have further questions, feel free to ask!