Currently docstore Index only keeps track of whether a docstore entry exists or not and the current value coinciding to it. There could be a toggle that turns on and off the past history tracking when the store instance is created. History would contain pasts queryable values, deletion, creation. This would be essentially converting events from the oplog into a useable format.

Side note: in the future the index could only store event meta, such as add, del. Values would be stored on disk/IPFS to conserve memory. Potentially even sharded (at the cost of performance) to save space.

I am willing to submit a PR to add this feature.