dont know about caching strategy for user-generated content. maybe something simple?

hey folks, i'm designing a platform where users can upload images and short videos. we expect high read traffic on this content. i'm considering different caching strategies to serve this content efficiently. should we go with a cdn approach with ttls, or an in-memory cache like redis for frequently accessed items? what are your thoughts on cache invalidation for user-generated content, especially when updates or deletions occur? looking for practical experiences and any pitfalls to avoid.