>Somewhat ironically Elasticsearch would probably work really well for this too (just make sure your elasticsearch isn't open to the world on the internet!).

Sure it will work, but I personally don't like Elasticsearch for anything high-intensity because of its HTTP REST API and the overhead it carries. Take a look at Cassandra's [1] "CQL binary protocol", it simple and always on point.

[1] https://github.com/apache/cassandra/blob/trunk/doc/native_pr...