I already get rate-limited like crazy on lemmy and there are only like 60,000 users on my instance. Is each instance really just one server or are there multiple containers running across several hosts? I’m concerned that federation will mean an inconsistent user experience. Some instances many be beefy, others will be under resourced… so the average person might think Lemmy overall is slow or error-prone.
Reddit has millions of users. How the hell is this going to scale? Does anyone have any information about Lemmy’s DB and architecture?
I found this post about Reddit’s DB from 2012. Not sure if Lemmy has a similar approach to ensure speed and reliability as the user base and traffic grows.
https://kevin.burke.dev/kevin/reddits-database-has-two-tables/
The part that worries me about scalability in the long term is the push nature of ActivityPub. My server is already getting several POST requests to /inbox per second already, which makes me wonder how that’s gonna work if big instances have to push content updates to thousands of lemmy instances where most of the data probably isn’t even seen. I was surprised it was a push system and not a pull system, as pull is much easier to scale and cache at the CDN level, and can be fetched on demand for people that only checks lemmy once in a while.
I think there’s a benefit to the push model, as the instances can prioritize who to push to first if there’s scaling issues, instead of having to throttle GETs, effectively the end result is anyway the same that nothing ends up to other instances in real time (which is fine). I don’t know how lemmy works exactly, but could the push model just be a detail of activitypub https://flak.tedunangst.com/post/what-happens-when-you-honk ?
It definitely is part of the ActivityPub protocol, but I only glanced at the spec so far. I should probably follow that link and implement a toy ActivityPub app to get more familiar with how it works.
I think there’s a benefit to the push model, as the instances can prioritize who to push to first if there’s scaling issues, instead of having to throttle GETs,
The downside to this is smaller instances are penalized in that scenario, which would in turn could cause users to flock to megainstances until it becomes centralized again.
As I said, GETs are cacheable, so if one slaps Cloudflare in front you can handle millions of GETs for relatively cheap.
Maybe it’s batched however? I really need to read the spec. Pushing to thousands of servers every 1/5/10 minutes certainly would give a fair amount of headroom to make it work I guess.
