SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac749b367d3ce42f3aeffd171bebd2b4c408d3ea893357b3552ae3f5f75e66fb' 
  AND token = 'lcSW+CzWB7i4GHz1ZaXKzfGYrI9ahaoSynHSgSHE7sA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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