SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a39f85d763b2ba07547b2daeea9c8b11c6666c586e8ff76f8ea590e900f8a921' 
  AND token = 'FPjc3hvsmXBKI6lLIckqvKGDfhChjldrk3B1L/skhvQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}