All mongos processes are present in the config.mongos collection (both on the config servers and the mongos processes). This collection contains the hostname/port of the mongos, the last ping time, and other information that is used by Cloud to understand the customer's cluster topology. This collection is missing while using the embedded router. Without this collection, as an example, monitoring discovery will only be aware of one router (the one used as a seed node to import the cluster) and will not be able to find out about the other routers in the cluster.