When will data be on more than one Shard?
MongoDB Sharding is range-based. So all the objects in a collection lie into a chunk. Only when there is more than 1 chunk there is an option for multiple Shards to get data. Right now, the default chunk size is 64mb, so you need at least 64mb for migration.
🔗Reference : stackoverflow.com
🔗Source: Azure Interview Questions and Answers