This is some feedback on the GraphQL API for anyone who cares to read it.
We love how fast GraphQL is, and how easy it is to use. We went all in and converted about a dozen of our requests to GraphQL. However, they often return a 504 error like the one in the attached image. So we had to remove them all except the submissions node. It appears to be the only one that is stable enough for production use.
I hope the feedback helps. As far as I can tell, this is a problem on the Canvas side and has nothing to do with our code, but, if I am wrong, I'd love to know.