More updates: Okay, so I got a bit excited and started learning C. I wrote just enough to read records from aligned log, and to seek for bipf values. I wrote a program that scanned the entire log and dumped every text content to stdout. It runs in 0.6 seconds on my laptop, and 6 seconds on nexus 5. (on the nexus that's reading 58 mb/s while also writing 10 mb/s!)

I think this is very strong evidence that a fast enough embedded database is entirely possible on mobile.