Graphql is not very convenient when it comes to uploading files, but it is possible, for example, gem apollo-upload-server-ruby is often used for this purpose.
In the world of Ruby development it’s accepted practice to test your code, but only a few people do performance testing. Such tests help to prevent the program work from slowing down while the amount of data grows, and they also help to understand whether the code performance has become slower after the recent code amendments.