SERVER-47359 added a new map '_connStringLookup' that stores mappings from connection strings to Shard objects. We saw a decent perf hit after SERVER-47359 was committed. A small and easy fix to gain perf back is to change '_connStringLookup' to store connection strings as std::strings instead of ConnectionString objects to avoid having to parse the "shardId" parameter passed to ShardRegistry::getShard and ShardRegistry::getShardNoReload to a ConnectionString each time.