A server system (100) for processing a virtual space, the virtual space comprising a plurality of entities (A-E), the server system (100) comprising: one or more back-end servers (108); and one or more front-end servers (114); wherein each back-end server (108) stores a respective subset of the plurality of entities (A-E); each front-end server (114) is communicatively coupled to each back-end server (108); each front-end server (114) is configured to be communicatively coupled to one or more client devices (106); each front-end server (114) stores one or more entity references (RefA-RefE); and each entity reference (RefA-RefE) comprises a first identifier for identifying a respective entity (A-E) and a second identifier for identifying the back-end server (108) on which the entity (A-E) identified by the first identifier is stored.