this discussion makes me think of something too... so, i already have a simple size-related caching strategy implemented, it runs on a timer and trims down the database when it gets to a certain size and trims it back to a second size (high and low water marks)
it might be an interesting addition to the cache prune heuristic to selectively prefer to remove entries that have few inbound references, ie, the less engagement, AND the more stale (last accessed timestamp) combined would be a good heuristic for pruning not just stale events but irrelevant events, which are going to largely be botfarms