But then if you keep the components simple - Postgres is a well-trodden path, for example, then you still manage to lop off a lot of complexity. And then of course you can keep the composition simple too - maybe you just need three thumping great Debian boxes running Postgres in three locations, maybe you just need some IPSec tunnels (complex to set up but again a well-trodden path) between them instead of what the latest SDN hawtness is, and so on.

The 80:20 rule still lives.