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 Mentioned

ActiveAdmin: 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.

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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.