Funny enough, this is a system design question asked in many interviews:

https://www.educative.io/courses/grokking-modern-system-desi... https://leetcode.com/discuss/interview-question/system-desig...

I've never designed such a system, but these are "baseline" solutions. It'd be interesting to see if anyone's actually implemented some of these canonical system design solutions and saw how well they actually scaled.