MongoDB 4.2 introduced the FlowControl feature. However, it might be interesting to have something that makes this node hidden or take it out of the cluster when it starts falling behind the primary and/or other secondary nodes after a certain number of seconds.

There are the majority/local and other types of read concern, but this won't help.

For example: If I have 3 nodes and one is starting to fall behind (due to a backup for example), I want my mongoS redirecting the reads for the other nodes. Setting it to hidden permanent is not an option because I lose hardware resources for it most of the time (because the node will be available only for backup).