This is incorrect advice.
OP is referring to the Digital Ocean “pre-configured” Discourse instance. That is locked at 2GB for political reasons because they don’t want people using swapfiles.
Just follow our official install guide, then you can select 1GB RAM droplet which works perfectly fine, and enable a swapfile, which will only really be touched during upgrades when there is crazy memory churn.
512mb is NEVER supported and SHOULD NOT be used.