All terms
Glossary
API first
The interface is designed and agreed first, implementation and user interface are built against it afterwards.
The benefit is parallel work: whoever knows the interface can build the frontend before the logic is finished.
The second benefit shows during replacement. A stable interface lets you swap the system behind it without touching every caller.
How you notice it
- Several clients will use the same functionality.
- Web and mobile are drifting apart.
- A partner needs access to the system.
Frequently asked
Does API first slow the first release down?
Slightly, and it pays back on the second client. Agreeing the contract before implementation lets frontend and backend work in parallel and makes breaking changes visible before they ship. On a single client with no future plans, it is overhead.