Azure APIM as forward proxy

Question

I am looking for some design guidance in using Azure APIM as a forward proxy between backend services (such as function apps or logic apps) and external clients.

We have a function app that processes invoice requests (for an order previously placed) from a mainframe system, does some transformations and sends them to an external party via HTTP. I have two options with the sending process.

1. Store external HTTP endpoint as an app setting in function app and let function app send the transformed message directly to external party.

2. Send the transformed message to Azure APIM with the external HTTP endpoint set as the backend service (using set-backend-service APIM policy) and let APIM forward it to external party.

Now, are there are any real benefits with the second approach if the requirement is only to forward requests to external party from a security or operational standpoint? There are no requirements to enrich the outgoing message (add or remove headers, modify message body etc).

Personally, all I see is an extra hop with the second approach. But some of my teammates seem to think the second approach can offer some benefits in the way of analytics. There are some metrics available under APIM --> Analytics tab that lets you see the number of successful, failed requests etc. But I think this information is also available to Application Insights tied to the function app.

Just interested to see some insights around this so we can make an informed decision.

Answer 1

I guess using Azure API Management would be an over-engineering in your case, assuming the Azure Function is only going to be the caller of the Azure API Management instance.

Even though Azure API management provides analytics, url-rewrites, transformations, analytics etc - it makes more sense when you use it to govern the API. Ask yourself a question on, how many of the Azure API management functionalities are going to be leveraged fully in your case.

Remember Azure API management by design is an API governance tool where you can perform throttling, monetizing your API by giving access to it to different 3rd party with segregated subscription keys. In my opinion, Azure API management comes into the scene where you need to distribute some API to 3rd party applications, which clearly not in your case.