CDC with Sling: When Log-Based Works and When Query-Based Is Enough

Based on your detailed explanation, here's a summary of when to choose between query-based incremental replication and log-based CDC (Change Data Capture) for data synchronization:

Query-Based Incremental Replication

Use Cases:

• No Deletes: The source database never deletes rows or deletions are not important downstream.
• Soft Deletions: You can model deletions as soft-deletes with an application flag that gets picked up by incremental replication.
• Limited Privileges: Only SELECT privileges are available on the source database.
• Monotonic Update Key: The table has a reliable, monotonic update key for cursor-based synchronization.

Advantages:

• Simplicity: Easier to set up and maintain.
• No Additional Costs: Works with open-source tools without requiring additional state storage or paid plans.

Log-Based CDC

Use Cases:

• Deletes Matter: The source database performs deletions that need to be reflected in the target.
• Low Latency: Need near-real-time synchronization due to high write volume.
• No Reliable Update Key: No trustworthy update key available for incremental scans.
• Audit Trail Required: Need a detailed history of changes, including operations like insert, update

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