Best practice on index usage with timestamp

Question

I have a query to find period tasks, it runs calculation and scans the whole table.

UPDATE task SET status = ?
WHERE cron_hour != 0
AND (status = ? OR status = ?)
AND UNIX_TIMESTAMP(NOW()) - end_time > cron_hour * 3600

I think the last condition will not use the index on end_time, what's the best practice here?

Answer 1

create an index on ( cron_hour * 3600 + end_time )

then write check in the where clause as

AND UNIX_TIMESTAMP(NOW()) > cron_hour * 3600 + end_time 

but you might find an index on status to be more useful