Talk: Legendary DX

Keeping developers in the flow is critical. Techniques like live reload and Hot Module Replacement were invented for this purpose. In this talk, I introduce the next step in web DX:

🔥 Hot Data Revalidation 🔥

A triforce symbol with 🤩 on top corner, 🤓 on left corner, and ğŸ˜Ž on right corner

You can also check out the slides.


  1. I think my acting might have been too good 😅 I am purposefully misleading the crowd into thinking that loader changes are impossible to handle gracefully. I think most people got the joke, but I could have hammered it home a bit more.

  2. I forget to add a key to the <input /> element, causing whatsup to be erased during HDR. With the key, React can track the elements and persist React state more reliably. Remix uses the same method as Vite for handling React HMR updates: React Refresh So you can see for yourself that omitting the key will cause <input /> state to be lost with Remix, Vite, or any other tool that uses React Refresh.

  3. If hooks are added or removed from a component, React considers this to be a different component. That means React Refresh will lose state for that component when processing updates with hook changes. Again, you can try this out for yourself with Remix or Vite.

  4. HDR detects changes anywhere in your code that affect each loader. It could be changes to the loader function itself, or to any code dependencies of the loader.

  5. After the HDR demo, I talk about calling the dev tools from the app server. I should have first stated that to solve the mismatch problem, we need to (i) ensure the app server is running up-to-date server code, (ii) ask for updated data from the app server, and (iii) only process UI changes via HMR after we have that up-to-date data. The trivial way to coordinate code is to run them in the same process and call them in order. However, running dev tools in the same Node process as the app server has drawbacks. In the presentation, I mention this all in passing and jump straight into the drawbacks.

I cover points (2) and (3) in more detail in a separate video.

I also did a livestream with the reputable Kent C. Dodds where we setup HMR/HDR in some of his projects. At the time, the API was unstable, so things have probably changed since then, but the concepts remain the same.