How do you define the single source of truth in an integration project?

When CRM, ERP, e-commerce and support systems connect, the hardest question is not “how do we move the data?” but “which system owns this data?”

Define the source system

In which system is the customer address definitive? Who changes order status? Does one system only view another’s data, or update it? When these decisions are unwritten, integrations overwrite each other’s data.

Signs of a good integration

• Field mappings and transformations documented.
• Error and retry behaviour defined.
• Webhook and batch flows separated.
• Data delay reflected honestly to the user.
• Permission and sensitive-data boundaries preserved.

Integration is never finished once

Source systems change, fields are added, API versions renew. Without monitoring, contract tests and a change owner, a working connection silently decays over time.