LFC Delta Lake ACID Transactions 3

Question 1

At what interval does Delta Lake automatically create checkpoint files in the transaction log by default?

Accepted Answer

Every 10 commits

Answer

By default, Delta Lake creates a Parquet checkpoint file every 10 commits to allow faster state reconstruction without replaying the entire JSON log.

Question 2

When Delta Lake detects a write-write conflict during a concurrent transaction commit, what is the expected outcome?

Accepted Answer

The transaction fails and the application must handle the exception and optionally retry

Answer

Delta Lake throws a ConcurrentModificationException on write-write conflicts; the application is responsible for catching it and deciding whether to retry.

Question 3

Which Delta Lake operation is guaranteed to be atomic when renaming or replacing an entire table partition?

Accepted Answer

Using Delta Lake's INSERT OVERWRITE or replaceWhere option

Answer

INSERT OVERWRITE with replaceWhere is atomic in Delta Lake because it records the entire partition replacement as a single transaction log entry.

Question 4

What happens to readers querying a Delta table while a long-running OPTIMIZE operation is running on the same table?

Accepted Answer

Readers see the pre-OPTIMIZE snapshot and are unaffected

Answer

OPTIMIZE is a transactional operation; readers see a consistent snapshot from before OPTIMIZE commits and are never blocked or exposed to intermediate state.

Question 5

In Delta Lake, which scenario would cause a transaction to be classified as a 'blind append' and be allowed to succeed even alongside a concurrent write?

Accepted Answer

An INSERT that only adds new rows without reading existing data

Answer

A blind append (INSERT with no dependency on existing table state) never conflicts with concurrent writers because it does not read any existing data to determine what to write.

(LFC) Lakehouse Fundamentals Certification Practice Test

(LFC) Lakehouse Fundamentals Certification Practice Test

LFC Delta Lake ACID Transactions 3