I remember reading their blog post about how moving from pages router to app router in Next.js helped their SEO last year. This time they are moving from Next to React+Inertia.js because of growing bills from Vercel even though deploying the same app on your own VPS instead of relying on cloud provider would probably solve the issue. Nonetheless, I still don't understand their yearn for complexity - does book tracking app really need GraphQL, separate frontend framework and complicated build process or all that could have been solved by sticking to deploying monolithic RoR app with HTML templates on VPS from the very start?