What does Delta Lake provide to ensure consistent read and write operations in a Fabric lakehouse?

• A. Eventual consistency with no transactions
• B. Only batch writes
• C. Read-only mode
• D. ACID transactions with merges, upserts, deletes, and snapshot isolation.

Answer: (D)

Delta Lake ensures consistent reads and writes by using ACID transactions coordinated through a transactional log (DeltaLog). Each write is atomic and durable, so concurrent operations don’t produce partial or corrupted results. This enables safe execution of data modifications like MERGE (upserts), UPDATE, and DELETE on the same table. Snapshot isolation means readers see a stable version of the data as of a specific commit, even while writes are in progress, preventing to see in-flight, inconsistent states. This combination—ACID transactions with merges, upserts, deletes, and snapshot isolation—provides the reliable, concurrent data access that a Fabric lakehouse needs.