A primary takes 5,000 writes/s and replicates asynchronously, with the follower about 2 seconds behind. The primary's disk dies and the follower is promoted. Roughly how many acknowledged writes are lost?

Answer

About 10,000 writes. In review, anything from 6,670 to 15,000 counts as right.

The worked estimate

Everything inside the replication lag is gone: 5,000 writes/s × 2 s = 10,000 writes. Synchronous (or semi-synchronous) replication would lose none, at the cost of slower writes.

Numbers: Numbers to know.

Review this in your daily deck → All cards in Replication