{"id":"lsm-wal-before-memtable","text":"Every `put()` and `delete()` writes to the WAL before inserting into the memtable, ensuring no acknowledged write is lost on crash.","truth_value":"IN","source":"entries/2026/05/28/log-structured-merge-tree-lsm.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{"example":"def put(self, key, value):\n    self._wal.append(key, val_bytes)  # WAL first\n    self._memtable[key] = val_bytes   # then memtable"},"explanation":{"steps":[{"node":"lsm-wal-before-memtable","truth_value":"IN","reason":"premise"}]}}