Monitor Rails sites for 500s, Action Cable drops, and asset pipeline 404s.
What breaks on Ruby on Rails sites
Common failure modes
Asset fingerprint mismatch after deploy (404 on CSS/JS)
Sidekiq queue backlog ballooning quietly
ActionMailer SMTP timeouts during traffic spikes
Where these sites usually run
Heroku
Render
Fly.io
self-hosted Passenger
How Lemwatch detects a Ruby on Rails stack
Lemwatch fingerprints your stack on the first check — for Ruby on Rails that means X-Powered-By or csrf-token meta tag with Rails signature. Once detected, the Ruby on Rails preset turns on the checks that matter for this stack and skips the ones that produce noise.