Backend & systems·Consistency and replication
you write to one node, read from another a moment later, get the old value, and it is correct a second after that.
Eventual consistency
A guarantee that replicas converge if writes stop, with no bound stated on how long that takes. It is what asynchronous replication gives you, and it is fine for most read paths. It is not fine anywhere a user reads back their own write, which is why read-your-writes is usually bolted on top rather than assumed.