Optimizing ORDER BY

Question

I am trying to optimize this query that sorts posts by reputation field (1st) and then id field (2nd). Without 1st field query takes ~0.25

Answer 1

select * 
from (
  SELECT -- everything is ok here
  , CASE 
      WHEN p.created_at >= unix_timestamp(now() - INTERVAL p.reputation DAY) 
        THEN + p.reputation ELSE NULL END order_col
  FROM posts AS p
  WHERE p.status = 'published' -- the only thing for filter
  LIMIT 0,10 -- limit provided as well
) a
ORDER BY 
    a.order_col desc
    ,a.id DESC