postgreSQL db replication can be done across machines and data-centers--that's more of a cloud-centric model for scaling and redundancy, but if you want to be as production grade as a social network or financial institution, it might be desired to have the option to do offsite live replication. You can setup postgres in active-active so you could have a failsafe node that boots up and uses a remote copy of the db and just takes over... this is all much more detailed though for a pleb. Mostly, the advice for the node runner starting out is to do some reseach and pick a technology stack that is going to be the direction of least pain for studying and implementing, but in reality, any and all of the options can blow up.