I don't think Relay is used that much outside of Facebook. The community seems to have settled on Apollo. Personally I find Apollo over-engineered. When I couldn't delete things from the cache, because of a bug, and was faced with digging into the complex code-base, I ended up just using straight JSON with a HTTP client/fetch and caching in a simple JS object.

Other users of my API [1] just use straight HTTP with JSON as well. GraphQL clients seem to solve something we are not encountering. If urql [2] or gqless [3] work well when I try them I'd be up for changing my mind though.

[1]: https://github.com/kitspace/partinfo

[2]: https://github.com/FormidableLabs/urql

[3]: https://gqless.dev/