Similarly to SERVER-69770 , we should make the type of lock required to take the DatabaseShardingState be enforced by the API. One idea is to have two acquisition methods:

• One that takes the exclusive lock and returns a non-const DSS.
• The other takes the shared lock and returns a const DSS.
• All methods that modify the DSS (i.e. need exclusive lock) should be made non-const. All methods that do not modify the DSS should be made const.