Something that is occasionally handy (when running a long/app-breaking migration, upgrading the database, making some fundamental change to configuration, or in the event of a security incident perhaps) is the ability to quickly lock down the application with a 503 and a 'be back soon' page.

Used to use nginx/apache reconfig with a local file for this (e.g. via something like https://github.com/capistrano/maintenance), but more recently I've been configuring AWS ALB to respond with a static blob (ex. using terraform variables).

Doing it via the load balancer is probably not a very portable solution (Digital Ocean doesn't appear to support it)... maybe traefik entrypoints could be used for this.