Why does Multer does not release memory?

I am developing node application to upload files, I can see that when multer receives a request with file 200KB for example, it then holds 400KB in the memory and does not release it even after the request finishes until the app receives a new request and do the same with the next request.

[![Memory Usage][1]][1]

const multer = require("multer");const storage = multer.memoryStorage();const upload = multer({  storage: storage});const app = express();const port = process.env.PORT || 3002;app.use(express.json());app.post("/submitRequest", upload.single("file"), async (req, res) => {  return res.send('ok')});const server = app.listen(port, () => {  console.log(`Server is running on https://localhost:${port}`);});console.log('Server started at:', new Date().toLocaleString()); ```  [1]: https://i.stack.imgur.com/IFyEb.png