Mongodb – Security on MongoDB

Mongodb uses mmap for memory management, relies 100% on the OS memory management. This means whatever memory you have left it has a really high possibility will be eaten up by mongo cause the entire datafile structure is mapped to virtual address space (It is not certainly a problem while the paging between physical and virtual memory is not that dumb to break your system down).

While Linux will page out some parts of the physical memory, so not the whole virtual segment have to be in physical memory just the recently accessed parts (check this), depend on the usage pattern mongo can run without problem. If the OS will have to extensively page things mongodb will be slow. You can restrict the usage of the memory. I would recommend to use cgroups. For your probable workload memory usage you can check also this documentation to have some idea.

The replica set was setup with the internal AWS addresses. So when python connected with MongoReplicaSetClient and the server sent back the addresses it couldn't find the other members of the replica set.

You can update the replica set using rs.conf() to get the config and then rs.reconfig() to set your new configuration.

Or, as I did, add the internal AWS address to the server hosts file, which I was able to do because it was not the internal AWS IP that was used.