In this episode of On Rails, Robby is joined by Jay Tennier, Engineering Manager at Rainforest QA, where he's spent over seven years working across a long-lived Rails monolith and supporting services. They explore how Rainforest maintains their platform with a small team, and the practical decisions that come with that reality. Jay shares lessons from pulling microservices back into the monolith, why they wrap third-party services in adapters, and how they push analytics work to BigQuery instead of straining their Rails database. The conversation covers testing philosophy including "wet tests" over DRY abstractions, using dry-monads for complex service flows, and how celebrating code deletion has become part of their engineering culture.

Social + Web Presence

LinkedIn: https://www.linkedin.com/in/jaytennier/
GitHub: https://github.com/jaytennie/

Twitter/X: https://x.com/jaytennier
Bluesky: https://bsky.app/profile/jaytennier.bsky.social

Company/Org Links

Homepage: https://www.rainforestqa.com/

Tools & Libraries Mentioned
Active Record: Rails ORM.

BigQuery: Hosted analytics warehouse.

Cube.js: API layer for querying analytics data.

DRY-Monads: Structured success/failure flow.

FactoryBot: Test data factories.

Grape: Ruby API framework.

GoodJob: Background job processor.

Q Classic: DB-backed job queue.

Redash: SQL-based dashboards and reporting.

RSpec: Rails testing framework.

React: Front-end application framework.

Haml: Legacy templating engine.

Segment / Mixpanel: Event tracking pipelines.

Books Mentioned

Confident Ruby by Avdi Grimm

Exceptional Ruby by Avdi Grimm

Working Effectively with Legacy Code by Michael Feathers

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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.

In this episode of On Rails, Robby is joined by Kayla Reopelle, a lead software engineer at New Relic, where she works on both the Ruby Agent and OpenTelemetry RubyGems. They explore what observability means for Rails developers—not just as a debugging tool, but as a way to build clearer, more reliable systems. Kayla explains OpenTelemetry's vendor-agnostic approach to instrumentation and shares practical ways to experiment with traces, metrics, and logs in both production and local development.

GitHub: https://github.com/kaylareopelle

🧰 Tools & Libraries Mentioned

ActiveSupport::Notifications: Rails’ pub/sub API used for instrumentation.
AppSignal: Rails-friendly APM and error tracking.
AWS X-Ray: Distributed tracing for AWS services.
Datadog: Full-stack observability platform.
Elastics Profiling Spec: Donated profiling format for OpenTelemetry.
Grafana: Open-source dashboards and visualization.
Honeybadger : Error monitoring for Ruby apps.
Jaeger: Distributed tracing system (CNCF).
New Relic Ruby Agent: APM agent for Ruby and Rails.
ObservableGauge (OTel Metrics): Async gauge for snapshots like queue size.
OpenTelemetry Collector: Pipeline for receiving and exporting telemetry data.
OpenTelemetry Logger Bridge: Sends Ruby logger output to OTEL.
OpenTelemetry Ruby: Vendor-agnostic telemetry for Ruby.
OpenTelemetry Ruby SIG: Community group maintaining OTEL Ruby.
Prometheus: Metrics collection and storage.
Rack Middleware: Web middleware stack used in many Rails instrumentations.
Rails Structured Logging / Event Reporter: Structured logs built into Rails.

Send us a text

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.

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.

Send a text

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.