SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b473de5853d4a7eb1cf561a6f1d1ebc45f50d1fd9679ad1a8707293893783208' 
  AND token = 'fn8HkNKgd1Rc8eDt8yWzKUUg7D2Uh69TcUbPmahZOhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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