Simone Carletti: Rails at the Center of DNSimple

In this episode of On Rails, Robby is joined by Simone Carletti, CTO of DNSimple, where Rails has sat at the core of a globally distributed DNS platform since the company launched in 2010. Simone walks through how DNSimple's infrastructure is organized across three primary languages - Ruby on Rails, Go, and Erlang - each chosen deliberately for the role it plays: Rails powering the main application and API, Go handling the zone server, and Erlang running their custom-built name servers. He explains why Rails has remained central even as the platform grew well beyond a typical web app, and what it takes to keep a long-lived codebase healthy with a lean team of around 15 engineers.Tools & Libraries MentionedSidekiq: Background job processing (enterprise edition).RSpec: Testing framework.Knapsack: Parallel test suite splitting.Lograge: Structured JSON logging for Rails.ViewComponent: Component-based view layer for Rails.Hanami: Ruby web framework, used for portions of the DNSimple API.PostgreSQL: Primary relational database.ClickHouse: Analytics database for DNS query log processing.Erlang/OTP: Runtime for DNSimple's custom name server (ErlyDNS).Go: Language powering DNSimple's zone server.Docker / Docker Compose: Used to run the full DNSimple infrastructure stack locally.Cursor / Claude Code: AI coding tools adopted across the DNSimple team.Terraform / Infrastructure as Code: Used to manage DNSimple's own domains and GitHub repositories.Books MentionedEloquent Ruby by Russ OlsenDesign Patterns (Gang of Four)Send us Fan MailOn 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.