3 Mistakes I See in Early-Stage Rails SaaS Codebases

I've worked across a range of Rails/React SaaS projects, from ERP systems to marketplace integrations, and the same few issues keep showing up in early-stage codebases. Here are the three that cause the most pain later:

1. Business logic living in controllers It's fast to write, but it doesn't stay fast. Once a feature touches billing, permissions, or notifications, controllers become a tangle that's hard to test and harder to change. Pulling logic into service objects or models early saves months of pain later.

2. No background job strategy from day one Sending emails, calling third-party APIs, generating reports, all of it ends up in the request cycle "just for now." Then the app is in production, and a slow API call is timing out checkout. Setting up Sidekiq (or similar) early, even for a handful of jobs, makes it trivial to expand later instead of a painful retrofit.

3. Treating the database schema as an afterthought Missing indexes, no foreign key constraints, JSON columns used where relational data belongs. These don't hurt at 100 rows. They hurt at 100,000 rows, right when the product is finally gaining traction and can least afford a slowdown.

None of these are hard to avoid. They just require thinking about where the app will be in a year, not just what ships this week. It's usually a lot cheaper to build it right the first time than to refactor under pressure once real users depend on it.