Upgrading from Rails 7.2 to Rails 8 - The Latest and Greatest

A step-by-step guide to upgrading a Rails application from 7.2 to Rails 8, covering Ruby 3.4 upgrade with YJIT, Solid Queue as a Redis-free background job queue, Solid Cache and Solid Cable for database-backed caching and WebSockets, the new built-in authentication generator as a Devise alternative, PWA support, breaking changes (minimal), and deployment with Kamal 2. Includes decision guidance on when to keep existing infrastructure (Sidekiq, Redis, Devise) versus adopting the new Solid gems, plus conservative/progressive/aggressive migration strategies.