With Heroku's free tier gone, this is my work-in-progress configuration for a new ruby on rails apps that I want to run as cheaply as possible.

Here's the gist of it:

• Rails.cache uses :file_store
• Use SQLite for a database
• Use redis for sidekiq and actioncable
• Run Sidekiq in embedded mode
• Use disk_storage for ActiveStorage
• Run ActionCable's websocket server in embedded mode
• Use hatchbox to deploy all of my apps on a single VPS on linode/vultr/aws/digital ocean
• Use Cloudflare as a CDN

The main theme here is taking advantage of how cheap disk storage is on VPS providers (~$0.10 per GB) as well as Hatchbox allowing unlimited apps to be deployed on a single machine. The cost per months follows this formula:

cost = ($10 per server + VPS cost) / # of apps

So if I had 10 apps running a single $5 Linode server and each app would cost me $1.50 per month. 100 apps on a $40 server would cost my $50 / 100 apps = $0.50 per app.

Caveats

This stack does make some assumptions about the app ideas I have:

• a lot of reads and very few writes
• very small chance of going viral
• low to medium traffic
• wary of every gem you use to manage memory usage

And this stack does nudge coding your app a certain way to squeeze as many apps as possible in a single server:

• heavily use russian doll caching
• SQLite should be running in WAL mode
• Sidekiq workers should not do anything that requires a lot of compute (adding things together, reading files, etc).
• Remove cookies from page responses so that they can be cached in a CDN and use lazy turbo frames to fetch user specific content.

Possible further optimizations

This same configuration could be done on fly.io instances in addition to scaling down to 0 after hitting idle timeout. I learned about this here. Although I don't have a lot of experience optimizing rails boot times in order to respond to a waking request fast enough. Given what has happened to heroku, I'd bet that a simple VPS provider would outlast a niche platform-as-a-service.

If anyone is interested in a tutorial, let me know.
Thanks for reading!

I am partially running this stack (sqlite and file_store caching) in production today at reipricetracker. If you are concerned about performance, you can see the top left speed badge be adding ?rails=1 to any URL.