You don't need to use node to serve a harp site - you can just compile the files and use anything - harp compile
This is a container that has node and harp available, to compile and install the static site, that nginx serves.
On top of node and harp a few common gulp packages are included to provide a build pipeline.
You can use our container: docker pull xorcode/gulp-harp-nginx
Or you can build your own:
docker build -t your-name-here/gulp-harp-nginx .
docker push your-name-here/gulp-harp-nginx
After this - just add this Dockerfile to your Harp repo:
FROM xorcode/gulp-harp-nginx
WORKDIR /srv/www
ADD . /srv/www/
RUN harp compile
EXPOSE 80
CMD nginx
Push it to your docker server - and your server will use 4-6MB of RAM instead of 60MB.
To see an example working repo, take a look here.