Systems and methods for sharing a physical cache among one or more clients in a stream data processing pipeline are described. One embodiment is directed to a system for sharing caches between two or more clients. The system comprises a physical cache memory having a memory portion accessed through a cache index. The system further comprises at least two virtual cache spaces mapping to the memory portion, each of the virtual cache spaces has an active window which has a different size than the memory portion. Further, the system comprises at least one virtual cache controller configured to perform a hit-miss test on the active window of the virtual cache space in response to a request from one of the clients for accessing the physical cache memory. Furthermore, data is accessed from the corresponding location of the memory portion when the hit-miss test of the cache index returns a hit.