Sync Modes

When configuring data synchronization between two systems, you can choose between two primary sync modes: System of Record and External ID. Both modes support bidirectional sync, but differ in how records are matched and how identifiers are managed.

Overview

Mode	Identifier Used	Best For
System of Record	SOR Primary Key + External ID field	Centralized identity with one authoritative system
External ID	Shared External ID field	Decentralized systems with user-defined identifiers

System of Record (SOR) Mode

In System of Record mode, one system is designated as the authoritative source for record identity. The SOR’s primary key becomes the universal identifier used to match records across systems.

How Identifiers Work

• The primary key of the System of Record is the unique identifier for matching
• An external ID field in the non-SOR system stores the SOR’s primary key

Record Creation

Created in SOR

When a record is created in the System of Record:

1. The record syncs to the non-SOR system
2. The external ID field in the non-SOR system is set to the SOR’s primary key

PostgreSQL (SOR): INSERT → id=123
Salesforce: CREATE → external_id=123

Created in Non-SOR

When a record is created in the non-SOR system:

1. The record syncs to the SOR, which generates a primary key
2. The external ID field in the non-SOR system is updated to match

Salesforce: INSERT → sf_id=001xxx
PostgreSQL (SOR): CREATE → id=456
Salesforce: UPDATE external_id=456

Updates & Deletes

• Updates in either system are matched using the SOR primary key (via the external ID field)
• Deletes are propagated bidirectionally using the same matching logic
• Changes flow in both directions while maintaining the SOR as the identity authority

When to Use SOR Mode

Tip

Use System of Record mode when:

• You have a clear “source of truth” for record identity
• Records primarily originate in one system
• You want centralized ID management with bidirectional data sync

Example use cases:

• PostgreSQL as the SOR, syncing customer data to Salesforce
• Your application database as the SOR, syncing to analytics systems

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External ID Mode

In External ID mode, both systems use a shared external identifier to match records. Neither system is inherently authoritative - the external ID is the universal key.

How Identifiers Work

• Both systems have an external ID field
• Records are matched solely by this shared identifier
• Records without an external ID are not synced

Record Creation

With External ID

Records with an external ID sync normally:

PostgreSQL: INSERT external_id='CUST-001'
Salesforce: CREATE with external_id='CUST-001'

Without External ID

Records without an external ID are not synced until one is assigned:

PostgreSQL: INSERT external_id=NULL
→ Record is NOT synced

PostgreSQL: UPDATE external_id='CUST-002'
→ Now syncs to Salesforce

Updates & Deletes

• Updates are matched and synced using the external ID field in both systems
• Deletes are propagated using the external ID for matching
• Both systems are treated equally - no hierarchy

When to Use External ID Mode

Tip

Use External ID mode when:

• Records may originate in either system
• You have existing business identifiers (customer IDs, SKUs, etc.)
• You want full symmetry between systems

Example use cases:

• Syncing between two systems that both create records
• Using business-meaningful IDs (e.g., CUST-001, ORD-2024-001)
• Integrating legacy systems with existing identifier schemes

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Comparison Summary

Aspect	System of Record	External ID
Identity Authority	One system (SOR)	Neither (shared)
Primary Key Usage	SOR PK is source of truth	Not used for matching
External ID Required	Only in non-SOR system	In both systems
Records Without ID	Auto-assigned from SOR	Not synced
Best For	Centralized identity	Decentralized/shared identity

Choosing the Right Mode

Next Steps

• Getting Started Guide - Set up your first sync
• Field Mapping - Configure how fields map between systems