Most of the current MongoDB drivers support routing read queries to the lowest latency replica set member - this solves part of the problem.
Choice of database when planning a project is a more fundamental problem, knowing what to use and why - is the trade off for Riak / Cassandra worth it over MongoDB or even MySQL? This people decide on a per-project basis and of course when starting don't always make the right longer term choice.
Choice of database when planning a project is a more fundamental problem, knowing what to use and why - is the trade off for Riak / Cassandra worth it over MongoDB or even MySQL? This people decide on a per-project basis and of course when starting don't always make the right longer term choice.