Just out of curiosity, what is your hardware architecture for your API layer? Is it a middle layer that sits between the web app, various interfaces and the database? Or is integrated with the codebase, with different URLs exposing different interfaces (Web, REST, etc.)

When designing APIs from the start however, there are a few things to take into account. One is the way the API is designed. If you work from the data upwards, then you tend to end up with find grained APIs that allow a frontend to do anything, but with really poor performance and with many calls going back and forth between client and API. I promote ‘scenario driven design’ where you look not just at your data structure, but at the scenario’s that your clients are going to want to perform on them. For example ‘registering a user’ is a scenario that multiple clients could need, so you would create API calls to cate user registration, rather than having a CRUD api around your user object. This leads to better designed and better performing APIs.