What is an Interface (API) – Simply Explained?

An Image

An API works like a menu. It tells you what can be ordered and in what form it arrives. What happens in the kitchen is none of your concern – and may change without you noticing.

Without an API, it would be like going into the kitchen yourself and searching the fridge. This works until someone reorganizes the kitchen.

Why This Matters

Direct access to the database of a foreign system is the most common cause for integrations breaking after an update. An API is a promise: "These fields exist, and they are called this."

What Makes a Reliable Interface

• Documentation. What requests exist, what responses come back
• Versioning. Changes must not break existing users
• Access Control. Who is allowed to do what
• Error Handling. What happens if the other party does not respond
• Rate Limiting. Protection against overload

The fourth point is most often forgotten. An interface without retry logic loses data unnoticed.

The Practical Question Before Any Integration

Is there a documented API? If yes, the integration is manageable. If not, file exchange remains – functional, but slower, more error-prone, and not real-time.

This question should be clarified before estimating effort, not after.