http://ddinsights.net/tags/quorums/Recent content in Quorums on Distributed Data InsightsHugoen-usFri, 05 Jun 2026 09:00:00 -0700http://ddinsights.net/posts/quorums-and-tunable-consistency/Fri, 05 Jun 2026 09:00:00 -0700http://ddinsights.net/posts/quorums-and-tunable-consistency/<p>Many distributed databases — Dynamo-style stores like Cassandra and Riak — don&rsquo;t make you choose consistency once and for all. They let you tune it <strong>per request</strong> using quorums. The mechanism is simple arithmetic with surprisingly deep consequences.</p> <h2 id="the-setup">The setup</h2> <p>Each piece of data is replicated to <strong>N</strong> nodes. For every operation you pick:</p> <ul> <li><strong>W</strong> — how many replicas must acknowledge a <em>write</em> before it&rsquo;s considered done.</li> <li><strong>R</strong> — how many replicas you read from and compare before returning.</li> </ul> <p>The headline rule:</p>