The BearJS web app is built on Gatsby.

The reason I chose Gatsby is firstly, I love using React, secondly, I love using GraphQL. Gatsby has both out the box and is blazingly fast.

Gatsby, unlike traditional React apps, is pre-built into static assets at the build stage ready to be served up. Once a page is served on the client then react is re-hydrated and normal interactivity can occur on the client.

In the following talk Jason Lengstorf does a great job extolling the virtues of Gatsby: