When your organization signs in through Suite single sign-on, Relic needs a stable way to recognize which Tenant the request belongs to. The externalId is that key — it is the Suite-side organization identifier, copied onto the Tenant when the organization is first provisioned. Because it is marked unique, no two tenants can share the same Suite identity, which is what makes the data-isolation boundary reliable. You never type this value by hand; it is set automatically during provisioning and stays fixed for the life of the tenant. It matters mainly when reconciling Relic data against Suite, or when support needs to confirm that a Relic tenant maps to the correct Suite account.
Technical section
Data model, API, and internals — visible to developers.