Currently I’m using a small dataset (about 3500 records) on ElasticSearch and saw some strange scoring. Hits that should have exactly the same score had _almost_ the same score. Almost the same is kind of a problem since we sort our data on score and name. After some researching it appeared sharding was the issue here. With only one shard the problem is solved. If you want to know how I found out and what alternatives you have please stay tuned.
updated @ Sep 13: Zachary Tong pointed me to an article with a much better solution (read: the right solution 😉 ). I added the second to last paragraph to explain it.