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.

`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());

`