IntegrationBeginnerexternal-idupsert
What is an external ID and why use it in integrations?
Real World Scenario
Same Contact syncs from marketing tool daily. You prevent duplicate Contacts with external ID.
Expected Answer
• External ID is a custom field marked externalId and optionally unique
• Upsert operations match on external ID to update existing or insert new
• Systems agree on stable key—ERP customer number, UUID from source
• Simplifies idempotent integrations on retry
• Do not use external ID on fields that change value over time
Follow-Up Questions & Answers
Click to expand — each follow-up includes a direct, interview-ready answer
Salesforce Id exists only in SF. External ID is your cross-system business key known to both sides.
Architect Perspective
Upsert + external ID is the integration happy path—say it whenever sync comes up.