Give the number of 30-year-old users who were active in the events on 2016/5/2.
30-year-old refers to age = '30'; active refers to is_active = 1; on 2016/5/2 refers to timestamp = '2016/5/2 XX:XX:XX';
SELECT COUNT(T3.device_id) FROM app_events AS T1 INNER JOIN events AS T2 ON T1.event_id = T2.event_id INNER JOIN gender_age AS T3 ON T2.device_id = T3.device_id WHERE SUBSTR(`timestamp`, 1, 10) = '2016-05-02' AND T1.is_active = 1 AND T3.age = '30'