There's a nice breakdown of the usability and scaling challenges the Google Photos team went through with the redesign of their app. Creating a "scrubbable" infinite scrolling page, maximising screen real estate, while maintaining photo aspect ratio, with instant loading and rendering, with libraries of 250,000 photos or more. The compromises and engineering challenges they encountered are laid out with clear explanations. An interesting read.
https://rob.al/2NOPNo6
A peek under the hood