ARM processors have been around for a while. In mid-2015/2016 there were a couple of attempts by the community to port MongoDB to work with this architecture. At the time, the main storage engine was MMAP and most of the available ARM boards were 32-bits. Overall, the port worked, but the fact is having MongoDB [&]

https://www.percona.com/blog/2019/03/20/mongodb-on-arm-processors/