Scale of the data behind the service likely contributes. This data is fixed. Therefore it’s easily indexed once into a cache or memory. Your Gmail is ever changing which results in some lost optimization without dramatic cost increase.

Thank you! I tried to optimize scrolling through the photos the most. Avoided any virtualization library, used Cloudflare for image transformations and for caching, etc. The masonry layout and polish you see here is all https://news.ycombinator.com/user?id=walz though

Specifically at https://www.jmail.world/photos