There is a Paragraph in https://redis.io/topics/cluster-tutorial which says:
Redis Cluster has support for synchronous writes when absolutely needed, implemented via the WAIT command, this makes losing writes a lot less likely, however note that Redis Cluster does not implement strong consistency even when synchronous replication is used: it is always possible under more complex failure scenarios that a slave that was not able to receive the write is elected as master.
What I understand, Synchronous write is supposed to be working as follows: 1. Client Z sends data D to B 2. B sends data D to B1, B2 and B3 3. B waits for ack from B1, B2 and B3 4. B returns response success to Z
Where Z is a client, B is Master node of shard, B1, B2 and B3 are replicas of B.
My question is even in complex scenarios, how can it fails in Synchronous write as Synchronous write?