Check out this article in which the author was able to run an app written in java with 4MB RAM only using GraalVM:

https://sites.google.com/a/athaydes.com/renato-athaydes/post...

That clearly shows whats possible.

Hey, you should take a look at Gentics Mesh https://getmesh.io/. It seems to be a lesser known headless cms but still very powerful and fully open source.

You may want to take a look at https://getmesh.io/ - A fully open source headless CMS. It has a GraphQL and REST API so integration with React should be fairly straight forward.