Define the exchange before building it
Choose the records and fields involved, the direction of travel and the event that starts the exchange. Establish a stable identifier so the same customer is not created repeatedly. Decide which system is authoritative when both contain a value. The connected service's account permissions, API availability and limits form part of the scope; a familiar product name does not mean every feature is supported.
Give operators a way to recover
Requests can fail, arrive twice or be processed out of order. Agree safe retry behaviour and how staff see rejected or incomplete records. Keep authentication material outside public pages and ordinary logs, and limit the connection to the access it needs. Use a representative test to compare the source and destination records. Document who maintains the integration when fields, permissions or external service behaviour change.