Mongos is the MongoDB query router (https://docs.mongodb.com/manual/reference/program/mongos/) and all the recommendations tells you that you should run a mongos process locally along with the service it is going to use it.
For traditional applications that’s totally fine, but when you run it in containers you need to be aware of two things.
1- The dynamic nature of containers make the usage of mongos a bit inefficient
2- Mongos is not cgroups aware
Let me go into details: