API Β· INTEGRATIONS Β· RELIABILITY Β· 11 MIN READ
Reliable integration is not a script that runs on demo data, but a production flow that knows how to recognize, record and recover from an error.
Determine data ownership first
There should be an authoritative system for each entity. One system can be the owner of the guest, another of the reservation, the third of the financial document. If both ends freely change the same field, synchronisation becomes a competition where the last record wins for no business reason.
Agree on direction, identifiers, and mapping rules before writing code. In particular, document values that do not exist on both sides and how unknown statuses are treated.
Every important operation should be idempotent
A network connection may drop after the receiving system has already processed a request. The sender cannot tell whether the operation succeeded and has to retry. If that retry creates another booking or charge, the integration is not reliable.
Idempotency key, external identifier, and log of processed events allow the same request to be recognized and return an existing result. This is essential for bookings, payments, invoices and inventory changes.
Retry without idempotency is not a reliability mechanism; it is the possibility of duplicating a business event.
Not everything has to be synchronous
The user does not need to wait for five external services to confirm the internal record. It is often better to save the basic transaction, publish the event and process the related steps in the background. The message queue stores work while the external system is unavailable.
Use a synchronous call when the response is necessary for the next user decision, for example a final confirmation of availability. For notifications, CRM synchronisation or analytics, an asynchronous flow reduces system dependency.
Retry should have limits
Transient failures should be retried with increasing backoff. A validation error, an unknown unit or a denied authorisation will not disappear after ten identical attempts. The integration must distinguish transient failures from permanent ones.
After a defined number of retries, a message moves to a controlled error-handling queue. It should retain enough context for someone to understand the problem, correct it and restart processing.
Log is not enough without business context
A technical message such as βHTTP 400β rarely helps the operations team on its own. Link each error to the booking, property, channel and workflow step. The dashboard should show successful and failed messages, queue delays and recurring causes.
A correlation ID shared across services makes diagnosis faster. Sensitive data and credentials must never be recorded in logs.
The API contract is changing
An external system may add a status, change a limit or retire an endpoint version. The integration should tolerate unfamiliar extra fields while responding clearly when required data is missing. Contract tests and a test environment help identify changes before production.
Versions, deadlines and integration owner should be documented. "Once connected" does not mean permanently completed; API integration is the relationship between two products that develop at different paces.
Minimum production checklist
Before release, check authentication and secret rotation, timeouts, retry rules, idempotency, rate limits, identifier mapping, audit, alarms and manual recovery. Test for duplicates, out-of-order messages, and unavailable external service, not just the ideal flow.
An integration succeeds when the team no longer has to copy data manually and exceptions become less frequent and easier to see. If day-to-day work still needs another spreadsheet to track failed transfers, the system is not yet complete.