Examples of techniques for tracking client sessions in a publish and subscribe system using a shared repository are described herein. An example system includes a processor of a server to receive a connection request with a client identifier from a client a predefined policy for duplicate client sessions. The processor is to query a shared repository of the system using the client identifier. The processor is to also execute a set of actions based on the predefined policy, a query result including a detected duplicate client session from the shared repository, and a set of parameters.