My guess is that it won’t work with less than 1GB bc of spring boot, hibernate and all the rest of Java enterprise “microservice” goodness.
There's a raft of more sane choices these days like Play, Dropwizard, Vert.X etc.. They all use far less resources. Spring Boot is huge because it has to support a decade of obsolete junk, its far more than just a REST app framework.
Checkout TechEmpower's framework benchmarks https://www.techempower.com/benchmarks/#section=data-r16&hw=...
(I added filters to limit to Java+Go+JS+Python and limited DB to Postgres and Mysql)
Java and Golang lead the pack, with JS a distant second and most Python frameworks hanging out near the bottom
I've encountered plenty of spring boot microservices in my work and, from what I hear of other companies, it's not particularly rare.
Most of the time, if you have a team that's productive in Spring, a manager or lead will be happy to spend some extra memory and get more features shipped.
So you actually haven't tried to run an application with those libraries, and you don't even know what libraries that particular application is using, and here you are speculating about something you don't know and/or understand.