Hello,

Jotai v2.9.0 has been released with a new store implementation. Let's recap what it is. The store is where atom values exist. It's mostly an internal thing, but the store API is exposed for advanced usage. Conceptually, a store is a subscribable WeakMap. The original store implementation was designed before Jotai v1, and one of the goals was to branch states. So, there were garbage-collectable versions of stores. Jotai v1 had an experimental feature called versioned state. However, there were too many technical difficulties integrating it with React. So, in Jotai v2, we dropped that experimental feature. This allowed us to simplify our implementation and improve code readability. But still, it's not super readable. The store implementation was based on an immutable atom state designed for Jotai v1, which Jotai v2 no longer supports. That motivated me to re-implement the store from scratch. The new implementation is based on a mutable atom state. It was shipped in Jotai v2.8 as an experimental feature and, now in Jotai v2.9, it's the default. I hope it improves code readability, but I'm not sure. Also, it might improve performance a little bit, but I haven't confirmed anything. Feel free to challenge yourself by reading the new implementation and experimenting with it.

Happy Hacking.

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