SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f57bfedfb8abba89779f9851040d9f3e91b610c5367fef70622a659908e2d3f7' 
  AND token = 'ZfwRSHcbfYGyF/4Vmgn7bvCnxPgDvMIuDdy+ncaINP8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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