Why Business Systems Fail at the Integration Layer

Two systems can both have a valid customer record and still disagree. A CRM may own contact preferences while an accounting platform owns invoice details. Before we connect them, we need to agree which system staff should use to change each piece of information—and what the other system should do with that change.

A field-ownership matrix can be a simple list of fields, the system allowed to update each one, and any exceptions that need a person’s review. For example, if the CRM holds a customer’s contact email and accounting holds their billing email, decide whether these are separate fields. Treating them as interchangeable could overwrite the address the accounts team needs. Also state what happens when someone edits the same field in both systems before the next synchronisation: which value should survive, and who should review a conflict?

Test a timeout after the remote system has already written the record, an expired credential, an out-of-order update and an unknown tax code. For each case, check what staff can see, when automatic retries stop and how someone can recover the record manually.

For the invoice example, rehearse finding the invoice after the timeout and completing reconciliation without creating another one. For an unknown tax code, agree who corrects the mapping and how the affected order returns to processing. A retry cannot resolve a business decision that nobody has made.

Write these decisions into the integration contract: who owns each field, what counts as completion, which failures can be retried and who handles the exceptions. We want a reader of that document to understand how work resumes after a failure, as well as which endpoints the integration calls.