This is sort of a broad question. I suppose it depends a bit on the architecture of your application. In general, I would suggest that any application that has been previously deployed in a conventional cloud environment like Amazon AWS, should work just as well on a cloudlet at the edge.
Creating an overlay from the OpenStack dashboard was broken for a time, but if you pull down the latest master branch and reinstall your OpenStack++ environment, creating an overlay should work now. You can take the base VM, install your database (or whatever other packages you wish to install) and then have it generate an overlay. You should then be able to synthesize that overlay once you have it on a webserver.
You can also create an overlay using the
cloudlet CLI that is installed as part of the elijah-provisioning project. First you must import the same base VM as you did in the OpenStack dashboard with
cloudlet import-base <path to zip>. You can then issue a
cloudlet list-base command to get the ID and path to the imported base image. Finally, doing
cloudlet overlay <path to imported image> should allow you to interact with the VM via a VNC session and install any necessary software. When the VNC session is terminated an overlay will be generated.
Sorry for the delayed response.