1. A method comprising: at an application platform system that includes a first application system of a first user, a second application system of a second user, and a multi-tenant data synchronization system (DSS): the DSS configuring a first data synchronization instance for a first account of the DSS, responsive to a request provided by a chat application server system of the first account, wherein the first data synchronization instance manages a first reference state representation object for the first account at the DSS; the first application system storing a first local state representation object that corresponds to the first reference state representation object of the DSS, wherein the first application system is constructed to receive first reference state representation object update notifications provided by the DSS; the second application system storing a second local state representation object that corresponds to the first reference state representation object of the DSS, wherein the second application system is constructed to receive first reference state representation object update notifications provided by the DSS; the first application system of the first user transforming a first chat instruction of the first user of the first application system into a first state update, and modifying the first local state representation object to include the first state update of the first chat instruction; the first application system providing at least the first state update of the modified first local state representation object to the DSS via a first local state representation object update notification; responsive to the first state update, the DSS determining whether to modify the first reference state representation object of the DSS to include the first state update; responsive to a determination by the DSS to modify the first reference state representation object to include the first state update: the DSS modifying the first reference state representation object to include the first state update, and the DSS providing at least the first state update of the first chat instruction to the second application system of the second user via a first reference state representation object update notification; responsive to the first state update of the first chat instruction, the second application system of the second user modifying the second local state representation object to include the first state update of the first chat instruction, wherein state of a first chat channel of the chat application server system specifies the first user and the second user as participants of the first chat channel, wherein the first application system of the first user and the second application system of the second user communicate via the first chat channel of the chat application server system by providing to the DSS state updates of chat instructions to add chat messages to the first chat channel of the chat application server system.