Felt like shining a bit more light on the situation:
I have recurring events of the server freezing on me. It does become totally unreachable after some time. I have one Joomla stack and one LAMP stack deployed using Bitnami. So far, i can't recall a similar situation on LAMP stack, but i'll keep monitoring. As for Joomla stack, here's how the freeze manifests itself:
CPU load (1 virtual CPU machine, stuck at around 9%):
Disk bytes (SSD disk, constant at ~21 MB):
Disk operations (at around 400):
Joomla uses APCu cache and has PageSpeed enabled. I will try to disable it and test for a week to see if the issue resurfaces. Will keep you updated...