More generally, 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. (In our example, n = 3, w = 2, r = 2.) 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. Reads and writes that obey these r and w values are called quorum reads and writes [44].vii You can think of r and w as the minimum number of votes required for the read or write to be valid.
