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How does an API integration work?

APIIntegrations

An API integration sounds technical, but the idea is simple: two systems exchanging data on their own, without anyone copying things by hand. Here is how that works and what matters when you have one built.

What is an API?

API stands for Application Programming Interface. It is the agreed way a system accepts requests and returns answers. Think of it as a menu: the system shows which data and actions are available and in what format you ask for them. You do not need to know how the kitchen works to place an order.

How an integration works, step by step

A typical integration runs through a few steps:

  1. Request. System A sends a request to system B’s API, for example “give me the status of order 1234”.
  2. Authentication. System B checks a key or token to confirm the request is allowed.
  3. Processing. System B looks up the requested data or performs the action.
  4. Response. System B returns a structured answer, usually in JSON.

This happens in milliseconds and can run thousands of times per minute.

Where it goes wrong in practice

The happy path is not the hard part. A good integration plans for the edge cases:

  • The other system is briefly unreachable (retries and timeouts).
  • A request arrives twice (idempotency, so you do not bill someone twice).
  • The data is wrong or the format changes (validation).
  • You need to see what happened when something breaks (logging and monitoring).

That is the difference between an integration that works in a demo and one you can run a business on.

Types of integration

Most integrations use a REST API over HTTP because it is simple and widely supported. For real-time updates, webhooks are common: the other system sends a message the moment something changes, instead of you polling for it. For traffic between internal services, GraphQL and gRPC are popular choices.

In short

An API integration lets systems work together automatically and reliably. Designing the happy path is quick; the value is in the error handling, security and monitoring around it.

Want to know what it costs to have one built? Read have an API built or see my services.

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