I just deploy Postgres and my app with docker behind Traefik loadbalancer for docker containers as I mentioned to you in this thread:
I deploy with a small bash script from my computer.
I build the VM in digital ocean with an init script, therefore when it comes online its already secured, as I mention here:
It’s good for deploying without too much downtime or no downtime at all.
In the case of Traefik it allows me to run many apps in docker and have Traefik managing TLS certificates automatically for me. I just need to start the docker container with some Traefik labels 
Don’t think about scaling until you need to. One VM can get you pretty far. Most hosting companies let you upgrade your VM to a higher tier with very small downtime.
In Digital Ocean and Linode you have floating IPs, therefore you can setup a new VM and when it’s ready you just switch the internal IP associated with the floating IP, thus the downtime is seconds.
Possibly a silly question: would this new VM retain the data from the old VM? I’m just thinking about this in the context of a DYI DB solution where I’d spin up a postgres instance pointing to a particular location on the VM.
Worst come to worst, you have to shut down the VM, migrate the VM image to another physical machine in the same data center. boot up the new VM in the higher tier, retain the old IP. The provider will handle all this for you, and the whole process take a few minutes.
If you want to migrate the data your self, you can flip a switch in postgres config, reload the DB config (a few seconds)
Then replicate the data to a new DB server. The replication could take over night in the worse case but your service is up all the time. Then you take down the old server, assign the old IP to the new DB server, and reboot the new DB server. In this case you will have 2 downtime, each maybe 15 seconds.
All of the above are solved problem that exists for years. You are not going to do this very often anyway.
For a new VM you need to copy the data from the old VM or instead you can try to use data volumes, that both DigitalOcean and Linode provide at additional cost. They are like external disks, thus you can swap VMs and always point them to the same disks.
Unless I have very specific requirements, I lean to the managed options whenever possible because they save a lot of time. Same with hosting.
I can do it all. I’d just rather spend my time elsewhere.
