https://nalar.dev/tags/isolation/ Recent content in Isolation on Nalar Hugo en-us Wed, 02 Sep 2026 00:00:00 +0700 https://nalar.dev/understanding-write-skew-and-transaction-isolation/ Wed, 02 Sep 2026 00:00:00 +0700 https://nalar.dev/understanding-write-skew-and-transaction-isolation/ <p>Transaction isolation is often explained with dirty reads and lost updates, but another anomaly is especially important for multi-row business rules: write skew.</p> <p>Write skew occurs when concurrent transactions read the same valid state, make decisions independently, and update different rows in a way that produces an invalid combined state. Because they do not overwrite the same row, ordinary write-conflict detection may not stop them.</p> <h2 id="a-simple-invariant">A simple invariant</h2> <p>Imagine an on-call table where at least one doctor must remain available:</p>