How does UDP maintain data integrity without an acknowledgement? If I’m sending a video from server to client, how can I be sure as a client that I’ve received the entirety of the video (or whatever other media), and that I’m not missing anything?
In short, UDP alone does not maintain data integrity. Most of the streaming audio or video that we consume ON DEMAND runs over HTTP which uses TCP and when packets are dropped, we get the dreaded "spinner" or "buffering". Services like YouTube or NetFlix identify these packet drops and lower the streaming bandwidth and thus quality.
For real-time video, UDP is preferred because it’s lower overhead and faster plus it works in multicast scenarios…think streaming a live sporting event to hundreds of thousands…the ACK from TCP from each of the clients would be horribly inefficient.
Now, if you really want to go down the streaming rabbit hole, look up RTCP, RTP and RTMP which are all media protocols that can dynamically switch between TCP and UDP. You would likely see these on the exam, except maybe know that CloudFront does support RTMP distribution.