Features are disclosed for detecting an event in input data using a cascade-based detection system. Detection of the event may be triggered at any stage of the cascade, and subsequent stages of the cascade are not reached in such cases. Individual stages of the cascade may be associated with detection thresholds for use in triggering detection of the event. The sequence of stages may be selected based on some observed or desired operational characteristic, such as latency or operational cost. In addition, the cascade may be modified or updated based on data received from client devices. The data may relate to measurements and determinations made during real-world use of the cascade to detect events in input data.