API Development for Business: Planning, Security and Integration

An API (application programming interface) lets one system talk to another: your website to your CRM, your app to your database, your accounting system to your payment provider. In business software, the API is often the longest-lived part of the system, so it deserves design time.

Start with the consumers and resources

List who will call the API (your mobile app, partners, internal tools) and which business objects they need: customers, orders, invoices, shipments. Name resources and actions in the language of the business, not of your database tables.

Design decisions that matter

• Authentication and authorisation. Use a standard such as OAuth 2.0 or scoped API tokens. Check permissions on every request, per resource.
• Versioning. Decide how you will change the API without breaking existing clients (for example a version in the path or header) and how long old versions live.
• Consistent errors. Return clear status codes and machine-readable error bodies.
• Pagination, filtering and rate limits. Protect the system and give clients predictable behaviour.
• Idempotency. For payments and orders, make repeated requests safe.
• Webhooks. Let other systems be notified of events instead of polling.

Document and test

Publish an OpenAPI description so clients can generate code and explore endpoints. Add automated tests for the contract, log requests with correlation IDs, and monitor error rates.

Integrating with third-party APIs

External APIs change, throttle and fail. Build integrations with retries and back-off, queue work that does not need an instant answer, store raw responses for debugging, and alert when a sync stops. Treat vendor credentials as secrets and rotate them.

If you need an API designed, or your systems connected (CRM, ERP, ecommerce, payments, accounting), see our API integration services.