SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '259e3bb15bf52a8ca8e28e71e9e1e4b91735faa37c2a15c6b5f26e845f3aac54' 
  AND token = 'p6dGuTbWpvNw0MZ+fU0Xi/v6dCjUJSJsr+xzOljV5LY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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