Connect systems with a clear contract.

Document required values, accepted formats and the meaning of relevant response states. Identify which system owns an identifier and how records are matched across the connection. Include examples of missing, unexpected and outdated values in contract tests. A successful connection does not establish that both sides interpret a field in the same way. Keep credentials and live customer information out of shared examples, and distinguish a test endpoint from production so a debugging exercise cannot accidentally create real fulfilment work.

Decide which failures may be retried, what limit applies and how a delayed result will be reconciled. Where the receiving API supports an idempotency mechanism, follow its documented contract rather than assuming that an arbitrary request identifier prevents duplication. If completion is uncertain, inspect the relevant remote state or use an agreed reconciliation process. A timeout alone is not proof that nothing happened. Preserve enough context to investigate the original attempt without placing sensitive request bodies in widely accessible logs.

A workflow may update one service while another remains unavailable. Record that difference and provide a route to resume or compensate for the unfinished work. Staff should be able to identify affected records, the last confirmed action and the person responsible for intervention. Test interrupted sequences as well as normal responses before release. The notes connect requests, recovery and data agreements through practical integration work. Predictable failure handling matters because connected systems will not always be available or return an answer at the moment the caller expects it.