API integration lets separate software systems exchange data under defined rules and security methods.
Connecting an e-commerce site to a payment provider, passing an order to a courier, sending customer details to a CRM or creating accounting records automatically are all examples of API integration.
API integrations reduce manual data entry and let separate systems behave like parts of a single operation.
What is an API?
An API is the interface that defines which data and operations a piece of software exposes to other software.
A payment API, for example, might expose:
- initiating a payment
- querying payment status
- creating a refund
- retrieving transaction details
- sending webhook notifications
Rather than granting direct access to the database, an API provides controlled and secure communication.
Where is API integration used?
- payment systems
- accounting and ERP
- shipping and logistics
- SMS and email
- authentication
- maps and location
- e-invoicing
- CRM
- social media
- marketplace integrations
- banking and finance
- AI services
What is a REST API?
REST is the architectural approach most widely used for exchanging data over the internet.
It typically relies on HTTP methods:
- GET: retrieve data
- POST: create a new record
- PUT/PATCH: update
- DELETE: remove
Data is most often transmitted in JSON format.
How is an API integration built?
1. Reviewing the documentation
Endpoints, parameters, authentication, data formats, error codes and rate limits are reviewed first.
2. Authentication
API keys, OAuth, tokens or signature-based methods may be used.
Keys must never be stored in plain text inside the code.
3. Field mapping
Each field in one system is mapped to its counterpart in the other.
4. Error handling
Connection drops, invalid data, unauthorised access and service failures are all handled explicitly.
5. Logging
Outgoing requests, incoming responses and errors are recorded securely.
6. Testing
Failure paths and edge cases are tested as thoroughly as the happy path.
7. Monitoring
Failed operations and performance are tracked in production.
What is a webhook?
A webhook is an automatic notification sent to another system when an event occurs.
When a payment completes, for example, the payment provider notifies your system directly, so there is no need to poll continuously.
Signature verification, duplicate-delivery checks and transaction identifiers are essential for webhook security.
API security
- using HTTPS
- token and key security
- scoped permissions
- IP or domain restrictions
- rate limiting
- data validation
- masking sensitive data in logs
- webhook signature verification
- preventing information leaks in error messages
Common problems in integrations
- incomplete documentation
- differing data formats
- service outages
- version changes
- timeouts
- duplicate operations
- currency and date format differences
- incorrect character encoding
- rate limits
- inadequate test environments
Integration therefore means more than establishing a connection: it means managing failure and outage scenarios too.
Can you integrate without an API?
In some cases file transfer, scheduled data exchange or a direct database connection can be used.
These methods need careful assessment for security and maintainability. Where no suitable API exists, asking the provider for integration support is usually the sounder route.
How Coreon builds API integrations
Coreon analyses the data flow between systems, the failure scenarios and the security requirements.
An integration is built around more than the successful request: service outages, repeated operations, failed verification and data mismatches are all accounted for.
Frequently Asked Questions
What is API integration?
It is the connection that lets two or more software systems exchange data in a controlled way.
Is a REST API the same as an integration?
REST is one approach to building an API. Integration is the act of connecting systems using that API.
Is API integration secure?
It can be made secure with proper authentication, HTTPS, authorisation and data validation.
What if there is no API?
File transfer or other methods can be considered, but security and long-term maintainability must be checked first.