notedeck itself doesn't really do any heavy processing. most of that is done by nostrdb in C in a threadpool (note parsing, sig validation, etc). all notedeck does it talk to the local relay and fetch things from the memory-mapped database with 0 serialization in and out since its all flatbuffers. the result is that the UI is 144fps+ consistent when scrolling. I built notedeck from the ground up with performance in mind. it even runs at max framerate on the slowest android devices I could find.