What an API is, in plain terms
An application programming interface, or API, is a set of rules that lets software systems communicate. Think of a restaurant: you do not walk into the kitchen. You give an order to a waiter in a standard format, and the waiter returns what you asked for. An API is the waiter. Your accounting system can ask your e-commerce platform for yesterday’s orders, or tell your CRM to create a contact, without anyone copying and pasting.
Common ways systems connect
| Method | How it works | Typical use |
|---|---|---|
| Request-response API | One system asks, the other answers on demand | Looking up a customer or creating an invoice |
| Webhook | A system sends a notification the moment something happens | New order placed, payment received |
| Scheduled sync | A job runs at set times to move data in bulk | Nightly inventory updates |
| File transfer | Files are exchanged in a set format | Legacy systems, partners, banks |
| Direct database access | One system reads another’s database | Last resort, with risks |
| Native connector | A built-in or marketplace integration | Common pairs of products |
| Integration platform | A tool that links many apps with visual workflows | Standard processes without custom code |
Concepts worth knowing
- Authentication. How a system proves who it is, through API keys or standard authorization methods. Treat keys like passwords.
- Permissions. What the connection is allowed to read or change. Use the minimum needed.
- Rate limits. Many APIs cap how many requests you can make per minute. Integrations must respect them.
- Pagination. Large result sets come in pages, and the integration must collect them all.
- Idempotency. Safe retrying. If a request is repeated after a timeout, it should not create a duplicate order or payment.
- Versioning. Providers update APIs and retire old versions, so connections need maintenance.
- Data mapping. Systems describe the same thing differently. A “customer” in one is an “account” in another.
Why integrations break
Most failures are mundane:
- An API key expires or is revoked when a staff member leaves.
- A provider changes a field or retires a version.
- A rate limit is exceeded during a busy sale.
- Data arrives in an unexpected format, such as a missing phone number.
- Two systems disagree about which is the source of truth.
- Nobody notices a silent failure for days.
Good integrations expect these problems. They include retries, alerts, logs and a place for failed records to wait for review.
Decide the source of truth
For each type of data, such as customers, products, prices and inventory, choose one system as the master. Other systems receive copies. Without that decision, edits in two places collide and data drifts.
Security basics
- Store credentials in a secure secrets manager, not in documents or code repositories.
- Use dedicated integration accounts with limited permissions.
- Encrypt data in transit.
- Log who accessed what.
- Remove access promptly when it is no longer needed.
- Verify webhook messages are genuine.
- Review what personal data is shared and why.
Questions to ask before building
- Does a native connector or integration platform already do this reliably?
- Which API features and plan levels do we need?
- What happens when a request fails?
- Who is alerted, and who fixes it?
- How will we test before using live data?
- What does the vendor promise about API stability and notice of changes?
- Who owns the documentation and credentials?
When to go custom
Standard connectors cover the common cases. Custom development makes sense when you need complex logic, several systems working in concert, higher volumes, stricter control or when no connector exists. Even then, build on standard tools and document it.
FAQ
What is an API integration?
It is a connection that uses APIs to move data or trigger actions between software systems automatically, replacing manual copying and exports.
What is the difference between an API and a webhook?
With an API you ask for information when you need it. With a webhook the other system notifies you immediately when an event occurs.
Why do integrations stop working?
Common causes include expired credentials, API changes by the provider, rate limits, unexpected data and unmonitored failures. Monitoring and alerts catch these early.
Do I need a developer to integrate my systems?
Not always. Native connectors and integration platforms handle many common cases. Custom or complex connections benefit from a developer.
Sources and further guidance
Platform features and requirements change. Check the linked primary documentation for your implementation.
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