If probably start with Node and RethinkDB... though plan on moving to separate data stores once you expand beyond what a few dozen servers can handle (around 10 million regular users).
A this point, you'll likely be using some que systems, a graph database implementation and likely Cassandra. Maybe Go to replace some burdensome node services.
When you need the next step after that (hundreds of millions of regular users), you'll have some custom solutions for your needs.
Stay modular and plan to replace everything you've built over time... that's the pragmatic way to go here.