My production server stack is Apache + some Ruby CGI scripts, to serve static files and handle billing webhooks. I spend less than an hour per week on devops maintenance.
KISS is the #1 principle when scaling a solo operation.
For the very few people who don't know mike or sidekiq, read this: https://www.indiehackers.com/interview/how-charging-money-fo...
Didn't ruby remove its CGI libraries from their standard library somewhat recently. I believe there were mostly helper libs, but I am curious how that works.
You don't need libraries. If you have reasonably low traffic CGI can get you really far.
And even after that, I would expect that CGI augmented with some careful caching (read: all static content and some dynamic content with sensible expiration policies) will get you even farther without having to dramatically change anything.