Status: IN
`SSIDatabase` adds a `_dependency_graph` and `_predicate_locks` on top of MVCC to detect read-write conflicts (write skew) that basic snapshot isolation permits
Source: entries/2026/05/29/topic-mvcc-snapshot-isolation.md
self._dependency_graph = {} # tx_id -> set of tx_ids
# on read:
if writer_tx_id is not None:
self._dependency_graph[tx.tx_id].add(writer_tx_id)