Is your 5us number from experience? Have you run SQLite on embedded before? Just hoping to hear some real world performance numbers for any hardware remotely similar!
I have run sqlite on a flash chip before (no filesystem, I suppose sqlite _was_ the filesystem) but I never took benchmarks. It was a 200MHz processor as well and it was basically fast enough out of the box that I never spent time on it. For 5uS response you have something like a thousand cycles to work with so any issue is likely storage related. I'd expect writes to be a bottleneck for example