Ask HN: How do you store and serve user uploaded videos?

I am working on a e-learning platform. Back end is in Java so I am using Amazon Java SDK to upload user uploaded course videos to a S3 bucket and serving them by reading from S3. However I notice that the users do not get the streaming benefit and videos do not start playing until all of video is downloaded.

What are you using for such use case and any pointers about how to serve large videos in a streaming fashion would be greatly appreciated, thanks.