@JustinDerrick @mattwilcox Yep, 100%! This is a drastic oversimplification but looking at what eats up memory and CPU on my server, the mastodon technology stack uses multiple services that work better the more resources you throw at them. Redis for instance can run on as little as 256 MB of memory and for small implementations, it's generally more than adequate. If you don't tune it though, Redis will basically say "Oh hey, this memory over here is free and I'm allowed to use up to 80% so I'm going to do just that."
Even though my instance only has 8 users, their interactions, who they follow, who those followers boost, etc. *also* plays in to the footprint as the server doesn't just store the data for its own users but the data on anyone that user has interacted with and that creates a massive footprint. For example, no one on my instance has shared any media files for about a week, yet the cached media on my server at this time is a little over 100 GB. That's because even though no one on my instance shared anything, they follow people who do, and that all gets cached locally.
So the distributed nature of the fediverse ends up being a double-edged sword.