The figure below shows the MongoDB system architecture. Briefly, Shards are MongoDB instances that hold a subset of a collection's data. Each shard is either a single mongod instance or a replica set. Config Servers are mongod instances that hold metadata about the cluster. The metadata maps chunks to shards. Router is a mongod instance that routes reads and writes from apps to the shards. Applications do not access the shard directly. The Config servers are set to 3 instances. Explain (1) the reason that Config servers need replications and (2) why the replications are 3 or at least 3? (Hint: consider the failover operations) (10 Marks) Application Server Router (mongos) Application Server Reads and Writes 2 or more Routers 2 or more Shards Shard (replica set) Router (mongos) Shard (replica set) 3 Config Servers Config Server Config Server Config Server