Provided are systems and methods for garbage collection of objects in storage. An example method may include providing a monotonically increasing logical clock. Each object is associated with a first number and a second number. The second number is a minimum of the first numbers of objects in a subtree to which the object refers. When the logical clock increases, objects with the first number less than the logical clock from the storage are deleted. When a new object is added to the storage, the first number of the new object is set to a new first number. The new first number is equal to or greater than the logical clock. The first number of each object in a subtree to which the new object is referring is updated. The updated first number is a function of a previous first number and a previous logical clock.