Yes this does seem almost exactly like what PeakSlab is doing. I'll have to investigate more how SSTables and memtables work to see if there's any improvements or anything to glean from them.

I'm storing null delimited sorted strings with an index that's an offset to where that entry begins, so if I wanted to do memtables for writing I would have to have two memtables and merge them on write? I've been considering this exact approach.