SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c828819559872850362c42d30f9e43c61d702d6f81e5bf9854539370cf33251' 
  AND token = 'HM7ohFcFpItO6YLfruXz8uFIwNNXszR4SdOHiqwRBNA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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