SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f4ba23613e2a18a4428c79e5d7ffeef2acdb3d8fe399c7f3da9db1e668d30ff' 
  AND token = 'MDmVgQtTVPdQ67qT1uM6py1v195UhVV9iguuk6W2gMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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