{"id":"mvcc-append-only-versions","text":"Writers never modify existing `Version` objects (except self-overwrites); new values are appended to per-key version lists, preserving the immutable snapshot for concurrent readers","truth_value":"IN","source":"entries/2026/05/29/topic-mvcc-snapshot-isolation.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{"example":"self._versions.setdefault(key, []).append(\n    Version(key, value, created_by=tx.tx_id))"},"explanation":{"steps":[{"node":"mvcc-append-only-versions","truth_value":"IN","reason":"premise"}]}}