Systems for managing user collaboration over objects stored on a cloud-based service platform. A server in a cloud-based platform maintains a set of read/write metadata that is associated in one-to-one correspondence to stored objects that are accessible by two or more collaborators. The server does not maintain a list of peers that communicate over peer-to-peer connections, rather the server exposes a semaphore for access to the metadata that pertains to a particular one of the stored objects. The server responds to download requests from the collaborators so as to deliver executable signaling protocol computer code to the collaborators' user devices. The signaling protocol code includes semaphore access by the collaborators' user devices using an application programming interface. Two or more accesses over the same semaphore establishes a leader and at least one follower. Corresponding ephemeral peer-to-peer connections are established between the leader and the at least one follower.