A leader has three followers. Which setup keeps writes fairly fast but still guarantees that every acknowledged write is on at least two machines?

Options

• ✗ Asynchronous replication to all three
• ✗ Synchronous replication to all three
• ✓ Wait for any one follower to confirm, and replicate to the others asynchronously Correct
• ✗ No followers, and a nightly backup

Why

This is semi-synchronous replication. Waiting for one follower costs about one round trip, and a single slow follower cannot stall writes, unlike waiting for all three.

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