It would be handy to have a method getIndex in drivers' APIs and in the mongo shell too.
This method would return a single index by name.

Currently there is a workaround to use findOne on system.indexes collection but as I see it's deprecated since version 3.0 and the suggested solution is to use listIndexes which forces me to iterate over the list when I want to find a particular index.

Here is a stackoverflow post that shows the need for getIndex method:
http://stackoverflow.com/questions/31456202/mongodb-getindex-amend-ttl-index