SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52940e505c54ebcd8010964c8aa521e72f39485e4a488636997655bb69ed914f' 
  AND token = '9yNYxBGOzVuJxA7sLKnwXks6ybnHz6fKvBbw19Dqang=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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