What are Read and Write Quorums?

A quorum is a minimum set of nodes that must respond to a request for it to be successfull
 
Write Quorum
A write is acknowledged by a majority quorum

Read Quorum
A read is acknowledged by a majority quorum

Majority Quorum typically has (n+1)/2 nodes when n is uneven and (n+2)/2 if it is even

With a quorum it is guaranteed that at least one of the responses to a read request is from a replica that saw the most recent write

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