[8n4vidtmkvmk]

I recently started ripping Mobx out of my app. Mobx solved exactly 1 problem for me, which was passing data horizontally (to siblings/cousins) and even to non-React components.

But now `useSyncExternalStore` solves that. No context needed. Can read and write state anywhere, even outside components. No "observe" or "track" shenanigans. Efficient updates (can listen to a subsection of the tree).

[spion]

valtio is a modern mobx-like implementation that uses `useSyncExternalStore` (via useSnapshot - https://valtio.pmnd.rs/docs/api/basic/useSnapshot).

Its still not quite as nice as MobX, as passing larger objects down the component tree means you need to mix snapshot and non-snapshot state. But it makes me hopeful about `useSyncExternalStore`

[mrj]

That appears to be in beta still? What store are you using with it?

I'll keep an eye on it! But mobx does more than that, like a lot of component optimizations and utilities. It's been so good for so long, I'm not in a rush to get rid of it.

[acemarke]

`useSyncExternalStore` was shipped live in React 18.0 and is fully ready for production use.

Source: I'm the primary Redux maintainer, and worked with Andrew Clark of the React team to nail down the semantics and behavior needed by `useSyncExternalStore` in practice. They had the idea, but discussed a lot of the necessary use cases with us and other lib maintainers, and a lot of its internal implementation is directly related to how React-Redux's `useSelector` hook was implemented already.

I built the first working code that used it by prototyping React-Redux v8's switch from our own internal subscription handling to `useSyncExternalStore` instead and gave Andrew feedback:

- https://github.com/reduxjs/react-redux/pull/1808