A Custom API Is Not a Thin Data Pipe. It Is Your Business Rules, Made Accessible.
When a mobile app or partner system needs the ERP, we expose purpose-built API endpoints rather than the raw database. External callers never reach the ERP directly — they pass through a middleware tier that authenticates the request, validates it, and forwards only well-formed calls.
The Rules Live Server-Side, and They Are Non-Negotiable
- An out-of-stock item returns an explicit error rather than a silent backorder
- A regulated product cannot be ordered without the prerequisite approval on file
- A payment must be confirmed before an order is allowed to advance state
- Every inbound request is authenticated and validated at a single audited choke point before it reaches the business system
The API is not a thin data pipe. It is the business’s rules, made accessible. A client application cannot talk the ERP into breaking its own logic, because the logic does not live in the client — it lives behind the endpoint.
Authentication Should Be Boring
Service-to-service credentials registered centrally, secrets stored in a vault rather than in code or setup tables, tokens refreshed before they expire, and a single audited place where every inbound request is validated before it reaches the business system. When authentication is interesting, something is wrong.
Scalability problems usually present as integration timeouts — an endpoint returning more data than the caller budgeted for, a function timing out on an unpaginated query. The fix is almost always pagination, batching, and explicit limits designed in before the volume arrives, not added after the first incident.