User_id   event_name        timestamp
1         process_now       08:00:01
1         process_now       08:00:02
1         process_now       08:00:03
1         fast_order        08:00:04
1         fast_order        08:00:05
1         process_now       08:00:06
2         process_now       08:00:01
2         process_now       08:00:02
2         fast_order        08:00:03
2         fast_order        08:00:04
2         fast_order        08:00:05
2         process_now       08:00:06
2         fast_order        08:00:07
2         fast_order        08:00:08
2         process_now       08:00:09

User_id   Event_name        timestamp
1         process_now       08:00:01
1         process_now       08:00:02
1         process_now       08:00:03
1         fast_order        08:00:04
1         process_now       08:00:06
2         process_now       08:00:01
2         process_now       08:00:02
2         fast_order        08:00:03
2         process_now       08:00:06
2         fast_order        08:00:07
2         process_now       08:00:09