The method below in my Java Spring application directly streams and uploads a file to an Amazon S3 bucket. I have researched that using streams will make the uploading of large files (> 100MB videos for my use case) to be more memory efficient. When testing the method with a 25MB file, the memory usage of my Java Spring application in a Kubernetes cluster setup spiked up by 200MB! I also tried a file that was 200MB and the memory spiked up again to ~2GB. There were no out of memory exceptions thrown but the memory usage does not drop back down. Why does this happen?

public void uploadFile(MultipartFile file, String saveFileName) {
        try {
            ObjectMetadata metadata = new ObjectMetadata();

            if (file.getContentType() != null){
                om.setContentType(file.getContentType());
            }

            metadata.setContentLength(file.getSize());

            saveFileName = saveFileName.replaceAll(" ", "");

            InputStream stream = file.getInputStream();

            PutObjectRequest request = new PutObjectRequest(bucketName, saveFileName, stream, metadata);
            request = request.withMetadata(om);

            s3client.putObject(request);

            stream.close();
        } catch (AmazonClientException | IOException exception) {
            // handle exception
        }
    }