Optimization: Top-N Per Group Pattern

Choose the more scalable way to fetch latest event per user. Query A: SELECT DISTINCT user_id, FIRST_VALUE(event_id) OVER (PARTITION BY user_id ORDER BY event_time DESC) AS latest_event FROM user_events; Query B: SELECT user_id, event_id FROM (SELECT user_id, event_id, ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY event_time DESC, event_id DESC) AS rn FROM user_events) t WHERE rn = 1;