Enclave scaling discussion

[BedrockSquirrel]

I'm not intending to merge this unless it becomes a useful record. I just wanted a place to discuss our options and planning for the medium- to long-term scalability of enclave DB.

Mostly I'm interested in whether we should start deleting historic batch data to keep things nippy and fleshing out the details of that.

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[BedrockSquirrel]

Closing this for now, we're just going to do the skip empty batches fudge for now to kick the can down the road but we need to come back to this soon.