I apologize if this question doesn't belong on this forum. If so, could you please point me in the right direction?
Here it is anyway:
When I add exactly the same key/object pair to the TreeCacheAop, the backstore BDB file keeps growing. There is only one node in the cache, the cache doesn't seem to change, but the DB file does, and rather quickly.
Is it normal?
Yes, I think so (though I'm not a BDBJE expert). AFAIK, BDB always appends modifications to the log (which is essentially the DB file). But there's a cleaner/compacter, which should (time or size-based) create new logs and truncate the old ones.
I suggest to check on the BDB forum for an answer.