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

On Rails

In this episode of OnRails, 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.

פרקים

1. Intro and welcome to Miguel and Peter from Gusto (00:00:00)

2. What keeps them "On Rails" and Rails' speed advantage (00:01:08)

3. The "biolith" setup and HIPAA compliance separation (00:02:51)

4. Working in the larger monolith versus benefits app (00:07:55)

5. Identifying boundaries when extracting services (00:10:15)

6. How Packwerk helps define and detect dependencies (00:11:28)

7. Why Sorbet transformed Packwerk's usefulness (00:13:47)

8. Enforcing boundaries Rails doesn't give by default (00:21:49)

9. Making Active Record models private with Explicit Active Record (00:26:56)

10. Rethinking database normalization and snapshots (00:34:47)

11. Temporal and bi-temporal data for audit trails (00:39:34)

12. Company Pool system for scrubbed production data (00:46:45)

13. How GraphQL federation affects service boundaries (01:06:10)

14. Rails as a Formula One car: fast but tricky with weight (01:12:20)

15. Book recommendations and learning by building (01:29:57)