Config servers all have the same process id of "ConfigServer."

On transition to primary, a config node unlocks all existing distlocks with the process id "ConfigServer."

This means that DDL operations which serialize on the config server via a distlock but whose business logic is executed by a shard (moveChunk, movePrimary, and shardCollection) are suspect, because the shard can keep executing the business logic outside the distlock. For example, you could drop a database concurrently with sharding a collection and end up with a config.collections entry without a corresponding config.databases entry.

Note that the track unsharded project will add two more DDL operations with the shardCollection pattern (renameCollection and convertToCapped).