[vvanders]

It's incredibly useful in read-only, memory constrained scenarios. I.E. we used to mmap all of our animation data on many rendering engines I worked on where having ~20-50mb of animation data and only "paying" a couple 10s of kb based on usage patterns was very handy. It becomes even more powerful when you have multiple processes sharing that data and the kernel is able to re-use clean pages across processes.

From reading the paper most of the concerns are around the write side. LMDB is the primary implementation that I know which leans heavily into mmap but it also comes with a number of constraints there(single writer, read locks can lead to unbounded appending to the WAL, etc). As with any tech choice it's about knowing constraints/trade-offs and making appropriate choices for your domain.