Is it possible to implement a mutex on a store where there are only set and get?

Question

Algorithms

Redis has a wonderful Redlock algorithm that allows you to reliably implement mutex (mutual exclusion) on distributed storages. But it is based on the insert-if-key-no ( SET ... NX) operation.
The question arose: is it possible to implement mutex based on storage VKontakte, where there are only operations set( key, value)and get(key)? There is a utils.getServerTime() method to get server time accurate to seconds.
The task is to coordinate several independent agents among themselves, so that at any time one of them will take on the task. The only connection they have with each other is through this VK storage.

Answer 1

No. The check-key-insert-new operation is not atomic.