API Designing Fundamentals

What will the API do What the user is expecting from the API What make the API easy to use

Bolt-On Strategy (For existing applications) Pros      faster - uses brute-force approach      takes advantage of existing code and systems Cons      existing problems in system and architecture can also come into effect in the API Greenfield Strategy (For new systems) Pros      Generally the 'API First' approach      can take advantages of new technologies and architectures Cons      Often hard to design      requires massive upfront investments Facade Strategy (For replacing existing piece by piece) Pros      mixture of above two systems      application is always functional Cons      can be challenging to have multiple approaches in the system      some behaviors can be hard to replicate.