1. A method for synchronizing between a primary control node of a storage system and a secondary control node of the storage system, the method comprises: performing a change in a key-value store that is stored in shared memory of the storage system and includes control metadata for controlling access to data stored in the storage system; the shared memory is accessible to the primary control node and to a secondary control node; generating a change indication that (i) is indicative of the change in the key-value store and (ii) requests the secondary control node to introduce changes in one or more additional data structures that are not stored in the shared memory; the change in the key-value store comprises replacing a previous given value with a current given value that is associated with a given key; wherein during at least a certain time period the previous given value and the current given value are concurrently stored within the shared memory at different locations; sending the change indication to the secondary control node; receiving an acknowledgement from the secondary control node; wherein the acknowledgement indicates at least one of the following: (i) the secondary control node received the change indication and (ii) the secondary control node introduced the changes in the one or more additional data structures that are not stored in the shared memory; and deleting, by the primary control node, the previous given value from the shared memory.