Same word, different data
Both systems may store a “customer,” while one means a person and the other a billing entity. Define record meaning, source identifiers and ownership before matching field names. Decide how time zones, currencies and empty values work. Rehearsing on representative examples before moving everything exposes silent errors earlier.
A repeated event should not repeat the business action
Providers can resend events when a response is missing, even if the receiving system already completed the action. A successful HTTP response alone is insufficient. Preserve event identifiers, design actions that do not repeat their business effect and expose conflicts. A repeated order notification must not produce a second shipment.
Assign an owner to the failure queue
Retrying every error indefinitely is not a strategy. Temporary outages and invalid data need different handling. Define retry limits, intervals and who investigates afterward. Keep event identifiers, status and error classes in operational records instead of customer descriptions or secrets. A technical failure should become a visible operational task.
Check the connection over time
Use periodic reconciliation between source and destination. Missing records, changed permissions and provider versions may not be visible through real-time alerts. Include API limits, version transitions and exports if the connection ends in the maintenance scope. Integration cost extends beyond the initial development hours.