under certain conditions, old items may be read instead of updated items

Under certain conditions, an older version of an item may be returned from a system.

With the move to WAL, marking items as clean before a commit can potentially lead to another reader fetching an old version of the item or not finding it at all. It would have to happen during a period of memory pressure, as the item would need to be marked clean, then ejected with the commit not having completed yet.