title: Rethinkdb slowed down drastically after adding a shard
body: <p>For a year we were working on single rethinkdb instance but couple days ago we were able to spin up a second machine and create a shard of the existing database on it.</p>
  
  <p>After tables (~60M of fairly simple records) finished balancing between shards we experienced extreme slowdowns in reads (reads are now, on average 10 times slower) and because of this - connection timeouts.</p>
  
  <p>The slowdown is visible in queries that use <code>between</code> on datetime fields. We tried both connections trough rethinkdb proxy and straight to one of the shards. There seem to be no speedup when connecting using proxy.</p>
  
  <p>Is this expected behavior? Can this kind of slowdown be avoided?</p>