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 Mentioned

Sidekiq: 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 Mentioned

Eloquent Ruby by Russ Olsen

Design Patterns (Gang of Four)

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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.

Simone Carletti: Rails at the Center of DNSimple

On Rails

Simone Carletti: Rails at the Center of DNSimple