I have a ES 7 cluster of couple of EC2 instances, the index has 6 shards and each shard has 2 replicas (so 1+2 x 6 = 18 shards for an index). When I create the index each shard size is around 25-30gb and we hold around 3mln of records in the database. We have a bit of updates happening everyday, let's say it's around 1mln, the update means the record gets replaced by a new one but the ID stays the same - we have pretty much the same amount of documents. I've noticed that after couple of weeks the shard size grows to 50gb so nearly double the size. Could someone please explain to me why this is happening and how can I fix it? (or should I fix it?) I've noticed search performance going down when we reach 50gb shards. Any comments/help would be highly appreciated.