How do you go about proxying REST style requests to a SOAP backend?
A harder case is when you have a "service" layer which also has a large collection of queries at various levels of abstraction.
These map poorly into resources, where you want a single level of abstraction per resource. And they map badly to legacy consumers, who've grown comfortable to having a collection of special knobs and dials perfectly shaped for their exact needs.
It does suck a bit, I've also sent Layer 7 into production which is just as bad as Axway. Typical Vendorware.
The AWS Gateway is pretty enticing. Solves lots of the API Gateway problem space very quickly and super cheap. We could run our production instance for about $2 a month I reckon, vs a 6 figure sum for the vendor tech.
[1]https://www.forrester.com/Sizing+The+Market+For+API+Manageme...
At a larger size, it may be more expensive than a roll your own, but for an independent idea that you just want to build something as a software/service and if successful be able to scale and handle extra load, it isn't a bad idea.
This is really the missing piece to Lambda in my mind... though being able to act as a bridge for legacy SOAP/WS-* services is pretty nice too. I've written a lot of pretty small node service that act as a bridge to SOAP based services the past few years... though most of those have been for internal use, and not sure how well that translates here.
Also API market is intended to grow to $660 million in US by 2020 and over a billion worldwide (http://blogs.forrester.com/michael_yamnitsky/15-06-07-the_ap...). So it's definetely not small.
Imagine this: You are BigCorp USA Inc. and have a bunch of internal SOAP-based web services that are 10 years old and cost a fortune to maintain.
You hear someone will pay you to use them, but SOAP sucks. So you could either go and change your APIs (and probably break a bunch of internal processes) OR you could use a gateway to sit in front of them and translate in bound / outbound requests. Now you can charge people for your APIs!
Scenario 2: If you're an indie dev/ startup but dont want to run EC2 infrastructure, Lambda + Gateway = Cloud service, without any heavy lifting, servers and cost effective. It's development lego. Kind of like Parse.
Scenario 3: You have an API for your app, now you wnat third party devs to use it.Your API is not set up for that kind of access (multi-user security, throttling, quotas, analytics etc.) - solution: shove a gateway in front of it.