> If I'm reading this right, you have 420M docs on a single shard? > Yep, you were reading it right.
Is Erick mentioned, it's hard to give concrete sizing advice, but we've found 120M to be the magic number. When a shard contains more than 120M documents, performance goes down rapidly & GC pauses grow a lot longer. Up until 250M things remain acceptable. But then performance starts to drop very quickly after that. - Bram
