Hi @Christian_Dahlqvist, up until the response by @DavidTurner, I knew nothing of the heap size, so it's whatever the default is.
Also (as explained in the last message) since the installation has used its own user for its resources, I'd prefer to not go changing ownership until I know it won't cause problems.
I'm running Ubuntu 18, and an application built on Vue, Express, Node, MySQL, Redis and so on, with PM2 to manage the restarting of things. I'm also running Kibana in the background, although I suppose that should be disabled.
As I said, I've been running the same instance since with a PHP application using Elastic 6.2 since 2014 without problems.