Nifty. I started from the part of the Umbra presentation that initially struck me as most interesting -- the allocator portion (where he talks about repeatedly MMAP_ANONYMOUS on the same address range to reduce fragmentation, etc.) I stopped working when I started pondering the bits about pointer swizzling and how I'd make that work nicely in Rust, and never got as far as the pieces that would actually do the syncs to disk.

I also came across another fellow who was inspired by the optimistic locking btree presented in LeanStore Umbra: https://github.com/NeowayLabs/bplustree