Too much MongoDB server memory usage when saving large file (3Gb) with GridFS.

Too much MongoDB server memory usage when saving large file (3Gb) with GridFS. Help fix, please.

let uploadStream: GridFSBucketWriteStream
let readableUpload: Readable

uploadStream = bucket.openUploadStream(chunkName)
readableUpload = new Readable()

readableUpload.push(req.file?.buffer)
readableUpload.push(null)

readableUpload.pipe(uploadStream)
new Promise((resolve, reject) => {
    uploadStream.on('finish', (g) => {
        readableUpload.destroy();
        resolve(g);
    });
    
    uploadStream.on('error', (error) => {
        readableUpload.destroy();
        reject(error);
    });
    
    readableUpload.on('error', (error) => {
        uploadStream.destroy();
        reject(error);
    });
});