[jstx1]

I don't work in this space, just passing by and wondering - what is an API gateway and when and why do use one?

[atmosx]

I believe the most common use cases are authentication, authorisation, rate limiting, smart routing, ssl termination, etc.

The idea is to offload these things to the API gateway instead of the backend application. Once the request _hits_ the backend the backend will _respond_ because the requests has been authenticated (login), authorised (rbac), etc. Implementation and responsibilities may vary. It is a pretty common pattern when using microservices.

[pestaa]

It helps with the operational side and the "boring" stuff: monitoring, logging, reporting, rate limiting, traffic control, endpoint versioning, etc.