Disclosed are systems and methods for processing events in an event stream using a map-update application. The events may be embodied as a key-attribute pair. An event is processed by one or more instances implementing either a map or an update function. A map function receives an input event from the event stream and publishes one or more events to the event stream. An update function receives an event and updates a corresponding slate and publishes zero or more events. Systems and methods are also disclosed herein for implementing a map-update application in a multithreaded architecture and for handling overloading of a particular thread or node. Systems and methods for providing access to slates updated according to update operations are also disclosed.