Miguel Conde & Peter Compernolle: Inside Gusto’s Rails Biolith

In this episode of On Rails, Robby is joined by Miguel Conde and Peter Compernolle from Gusto, where they work on a "biolith"—two distinct Rails monoliths serving 600+ engineers. Peter leads the HIPAA-compliant benefits domain, while Miguel is extracting the time product from the main monolith. They explore how Gusto identifies boundaries, manages temporal data, handles eventual consistency, and navigates the trade-offs of GraphQL federation.🧰 Tools & Libraries MentionedActiveAdmin: Admin UI for Rails.after_commit_everywhere: Run code after commits.Datadog: App and CI/CD observability.FactoryBot: Build test data.GraphQL: API layer for SPAs.Kafka: Event streaming backbone.Packwerk: Enforce boundaries in monoliths.PaperTrail: Model change auditing.React: Front-end framework.Sidekiq: Background job processing.Sorbet: Gradual Ruby types.TypeScript: Typed JavaScript.explicit_activerecord: Guard writes to models.Ruby Koans: Learn Ruby by practice.Cracking the Coding Interview: Interview prep book.Gusto Engineering Blog: Posts from Gusto engineers.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.