A 1st Stab at Correcting Bad Shard Key Selections MongoDB is designed to scale and handle very large data sets. You can scale vertically in your replica sets by adding resources such as CPUs, RAM, and disks. However, many applications today require more resources than can be added to a single server.  The next level [&]

https://www.percona.com/blog/refining-shard-keys-in-mongodb-4-4-and-above/