[troupo]

> But what really defines client side state?

You define it. And the client defines it.

> If the latency was good enough

It's never good enough. Worse, it can abruptly become not good enough. And you have to code additional loading states or optimistic UI for every action that is now performed on the server and takes longer than some time.

> It doesn't force you to give them the same state when they re-open your app

Then why would you store modal state on the server?

It's also a consideration of resource utilization. A million clients with their own app state is better than a million clients hitting your server and requiring you to store that state.

[andersmurphy]

Not if you care about state being consistent between all clients. Say you want a minimap, or a presence indicator, now the server needs to know these things. Same the minute you want backend analytics.

Millions of users hitting the same server at the same time is a very nice problem to have. I've handled 40000r/s (script kiddies are gonna script) with 500+ concurrent users in those demos on a 5$ VPS. With all the scroll position/tab state etc not just going to the server, but to a sqlite db.

Events up are fine if you batch them and 204 (i.e CQRS). In return you get a nice pushed based system that you can throttle/batch. You only push view data when the server decides to. In my case that's every 100ms (because it's a 5$ server), so all changes in that time get batched.

>Whenever your program has to interact with external entities, don't do things directly in reaction to external events. Instead, your program should run at its own pace. Not only does this make your program safer by keeping the control flow of your program under your control, it also improves performance for the same reason (you get to batch, instead of context switching on every event). Additionally, this makes it easier to maintain bounds on work done per time period.

- tiger style https://github.com/tigerbeetle/tigerbeetle/blob/main/docs/TI...

You don't need optimistic UI, a fast server with an in process DB and a decent backend language and you'll be fine for a lot of use cases. I like to add a pop animation on the client to register something has happened, but in a lot of situations you don't even need that.

[troupo]

> Not if you care about state being consistent between all clients.

No idea what you mean

> Say you want a minimap, or a presence indicator, now

I struggle to see where I said that you have to have everything and anything on the client.

> Events up are fine if you batch them and 204 (i.e CQRS). In return you get a nice pushed based system that

That you have to actually code, create, and maintain.

> Whenever your program has to interact with external entities, don't do things directly in reaction to external events. Instead, your program should run at its own pace.

No idea what this has to do with anything I wrote

> You don't need optimistic UI, a fast server with an in process DB and a decent backend language and you'll be fine for a lot of use cases.

Again, this hinges on the childish belief that the network is always there, is always fast, and is always low-latency.

And none of these answer the question of why you would want to save "I showed a modal on the client" in a backend database.