Integration of REST API with Lambda

Question

Hello,
I'm developing a REST API with API GW and Lambda (Java Runtime).
What would be the best way to integrate a Rest Resource with a lambda function? Of course I know how it is done technically but I need some architectural advice.
At the moment I see three possibilities:
1. I use quarkus and the EasyRest implementation, as known from the classic Tomcat environment. In other words, Jax-RS.
2. I write the logic myself that uses the path from the APIGatewayrequest object to determine which class should be called next.
3. i use a jar with one RequestHandler per resource and use this jar to create as many lambdas as there are resources in my API. The actual logic is integrated as a shared lib in each lambda via a layer. So the lambda itself is just a dumb flow heater connected to the rest of the resource.

Point 1 works, but somehow it doesn't feel right to recreate the complete API in the code - that makes sense in Tomcat, but now we have ApiGateway.
Point 2 sounds like pure desperation because there is nothing else ;-)
Point 3 sounds kind of right, but leads to a lot of lambdas. Unfortunately, a Lambda can only provide one RequestHandler, otherwise it would be easier.
What are your opinions on this?

Answer

Hi,

Thanks for your reply. This means that my idea from point 3 is a common approach?
Our AWS infrastructure is managed with Terraform Enterprise, so creating the Lambdas is not the problem.

Answer

Hi,

Option 3. is probably the way to go if you consider other aspects: Lambda does the "undifferentiating heavyweight lifting" for you (scaling, resiliency, runtime patching, etc.). Additionally, it allow very granular security (per lambda - It is harder to do with any Java AS like Tomcat)

So, you get more time to focus on our application.

Also, Lambda is pure pay-as-you go model: if unused, you don't pay. It would not be the case for Tomcat.

When you get to a high-load steady state, then you may start thinking about going back to a traditional AS-based architecture to optimize your costs via EC2 with FaaS.

Finally, on the number of Lambdas, it is not an issue if you implement from start the right Infra-as-Code tools like CloudFormation or even CDK. CDK will allow you to have a very sophisticated and fully programmatic approach to resource definitions.

Best,

Didier

Integration of REST API with Lambda

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