Feature Work

This mutex will only be used when accessing or changing the not-yet-created mutable shardVersions map. We don’t need it yet, but to shake out any potential bugs, place the mutex around all accesses of the current ShardVersionMap that exist on the RoutingTableHistory.

Testing Work

We won’t add additional tests for this step — we just want to make sure that read accesses don’t case deadlocks, so Evergreen will be sufficient.