SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '447670f2523eec7409004b965bd51a78e7fa753a99f3def35a190cf49d4ab284' 
  AND token = '40KnRGbyBVxOC4PgTGj66IWIzcYZl4B795pLbN/fVu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Impossible WHERE noticed after reading const tables