Quorum Reads and Writes

Note

Dynamo style model

If there are n replicas, every write must be confirmed by w nodes to be considered successful, and we must query at least r nodes for each read.

• As long as $w+r>n$, we expect to get an up-to-date value when reading because at least one of the r nodes we’re reading from must be up to date.
• r and w are like the minimum number of votes required for the read or write to be valid.