The main factor impacting the RAM requirement of the instance is the size of the data that you feed into it, especially if you need an in-memory index. (If you are curious about peak memory use etc., you can profile Pathway memory use in Grafana: https://github.com/pathwaycom/pathway/tree/main/examples/pro....)
One point to clarify is that "Pathway Community" is self-hosted, and the "8GB RAM - 4 cores" value is just a limit on the dimension of your own/cloud machine that the framework will effectively use. Currently, if you would like to get a "free" cloud machine to go with your project, we suggest going for "Pathway Scale" and reaching out through the #Developer Assist link - add a mention that you are interested in cloud credits. You can also go with 3rd party hosting providers like http://render.com/ who have a (somewhat modest) free tier for Docker instances, or reasonably priced ones like fly.io https://fly.io/docs/about/pricing/.