How does Delta Lake handle conflicting writes?

Delta Lake addresses conflicting writes through the use of optimistic concurrency control. This mechanism works by allowing multiple operations to occur simultaneously while monitoring for conflicts when the writing processes attempt to commit their changes.

When a delta table is modified, Delta Lake tracks the version of the data being accessed. If two transactions are in the process of writing to the same data, the system checks for any conflicting changes at the time of commit. If a conflict is detected—meaning that one write could potentially overwrite the effects of another—Delta Lake rejects one of the writes. This ensures data integrity and consistency, as only one version of the data is kept, and users are made aware of the conflict so they can take appropriate actions, such as retrying their operation or resolving the conflict manually.

This approach contrasts with mechanisms that overwrite data or enforce strict write locks, which can lead to bottlenecks and decreased performance. Through optimistic concurrency control, Delta Lake efficiently maintains the integrity of the data while allowing for concurrent write operations.