Exclusive (X) locks are used by read-write and read-only operations and provide a transaction with exclusive access to a key.

MaxDurability is the maximum value in the Durability enum.

None represents the absence of a lock or the intention to acquire locks.

Replicated locks are held on at least a quorum of Replicas in a Range.

Shared (S) locks are used by read-only operations and allow concurrent transactions to read under pessimistic concurrency control.

Unreplicated locks are held only on a single Replica in a Range, which is typically the leaseholder.

Upgrade (U) locks are a hybrid of Shared and Exclusive locks which are used to prevent a common form of deadlock.

Durability represents the different durability properties of a lock acquired by a transaction.

Strength represents the different locking modes that determine how key-values can be accessed by concurrent transactions.