Engineering Decisions · Senior · Question 6 of 14
A payments ledger must survive the loss of a whole region with zero lost writes. An extra 20 ms per commit is acceptable. Which replication do you choose?
- 1Nightly backups copied to a second region
- 2Asynchronous replication to a second region
- 3Synchronous replication to a second region
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Correct answer: Synchronous replication to a second region
Explanation
Synchronous replication confirms a commit only after the second region has it, so a region loss loses nothing, and the latency cost is accepted here. Asynchronous replication fits most products, keeping commits fast, but the last transactions are lost on failover. Nightly backups fit archives with a tolerance of hours, and for a ledger they would lose up to a full day.