I struggle to use lmdb when using resource isolation (like docker, nomad exec driver). The hidden complexities really become apparent when you build largish systems using shared infrastructure. Anything is easy if you have a dedicated machine or have dataset smaller than your memory allocation.
Mmap is so simple for the application/developer, but the price you pay is giving up clear ownership of memory and clean separation between kernel page cache and application space. The interaction between the mmu, mmap, tlb and the linux kernel IO layer is complicated. You don't want to touch that complexity at all if you care about ultra low latency.
The article rephrases the question into
"do you really want to reimplement everything the OS already does for you?"