Synchronous and asynchronous replication

Synchronous replication waits for replicas before confirming a write: no data loss on failover, but higher latency. Asynchronous confirms immediately: faster, but the last writes can be lost if the leader dies.

Where it shows up in real systems

  • Inter-region link

    Carries replication and service traffic between regions. Synchronous replication over it adds the full round-trip time to every write; asynchronous replication risks losing the last seconds on failover.

    In production: AWS Transit Gateway, VPC peering, Azure Global VNet Peering

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