1. A system to execute within a host organization, wherein the system comprises: a processor and a memory to execute instructions at the system; a broker to enqueue received messages; a push connection from the broker to a thread, wherein the broker is to push an initial message to the thread for processing; a pull connection from the thread to the broker, wherein the thread is to request one or more additional messages for bulk processing with the initial message from the broker; a query interface to issue a database query from the thread to a data store, the database query specifying the initial message and the one or more additional messages as a set of messages to obtain a lock for the set of messages; and a message processing engine to handle the set of messages in bulk based on whether the lock for the set of messages is obtained.