In this episode of On Rails, Robby is joined by Brian Scanlan, Senior Principal Engineer at Intercom, where a 15-year-old Rails monolith with millions of lines of code sits at the heart of the business.

Brian shares how Intercom's philosophy of being "technically conservative" has kept their engineering organization productive and focused on shipping product rather than managing infrastructure complexity, and on Intercom's all-in bet on Claude Code as their singular AI tool, now generating over 95% of daily code, with over 1,000 weekly users across the company including non-engineers in sales, marketing, and finance. Brian explains their approach to automated code review and PR approvals, how they built a Rails console MCP that lets Claude run production queries (with non-engineers as the top users), their layered plugin and skills architecture, and where AI still falls short in open-ended debugging, using the metaphor of commercial airline pilots who know when to disengage the autopilot.

Tools & Libraries Mentioned

Books Mentioned

Designing Data-Intensive Applications by Martin Kleppmann

Blog Posts Mentioned

Choose Boring Technology by Dan McKinley — https://mcfunley.com/choose-boring-technology

Send us Fan Mail

On Rails is a podcast focused on real-world technical decision-making, exploring how teams are scaling, architecting, and solving complex challenges with Rails.

On Rails is brought to you by The Rails Foundation, and hosted by Robby Russell of Planet Argon, a consultancy that helps teams modernize their Ruby on Rails applications.

Brian Scanlan: Building AI-First at Intercom

On Rails

Brian Scanlan: Building AI-First at Intercom