Ruby Talks: John Dewsnap on Moving Flexcar From Java to Rails in 4 MONTHS + Keynoting RailsConf 2025

Summary

John Denap, Director of Engineering at Flexar, shares his journey of migrating from a Java-based microservice architecture to Ruby on Rails in just four months. Speaking as the second keynote speaker at RailsConf, he discusses the challenges of switching frameworks with no prior Ruby experience, the support of the Rails community, and the positive outcomes of their decision. Despite initial reluctance, the team successfully adopted Rails, improving feature rollout speed and internal collaboration. The story highlights Flexar's transition, the lessons learned, and the impact of Rails on their development process.

Takeaways

• 😀 John Denap, the Director of Engineering at Flexar, discusses his experience keynoting at the final RailsConf after transitioning to Ruby on Rails from Java.
• 😀 Flexar made the major shift from a microservices architecture with Java to Ruby on Rails and a monolith, despite having no prior experience with Ruby or Rails.
• 😀 John shares how his team, initially reluctant, gradually embraced Ruby on Rails, with a focus on frontend development and tools like Turbo and Stimulus.
• 😀 The transition was prompted by challenges with their previous Java architecture, including long development cycles for new features due to many microservices and inter-team dependencies.
• 😀 Flexar's previous Java setup with 80+ microservices led to inefficiencies, such as slow feature releases taking up to 3 months, while Rails now enables quicker rollouts in a matter of weeks.
• 😀 The team adopted tools like Cursor to help explain architecture and facilitate smoother collaboration and decision-making during the transition.
• 😀 Despite initially fearing that switching to Rails might result in losing developers, the adoption was largely positive, with few people leaving the company.
• 😀 John discusses the welcoming nature of the Ruby and Rails community, which stood out to him at RailsConf, enhancing the experience of transitioning to the ecosystem.
• 😀 Rails proved to be forgiving during the learning process, allowing developers to adapt quickly, despite some initial code being written in a Java style.
• 😀 The migration process at Flexar, initially planned for 3 months, was completed in 4 months with a working application that went live at RailsConf, amidst a high-pressure situation.
• 😀 The success of the Rails migration at Flexar has had a significant impact on product development speed, team dynamics, and company efficiency, leading to faster feedback loops and quicker iterations on new features.

Q & A

What motivated Flexar to transition from a Java-based microservices architecture to Ruby on Rails?

The decision to move from Java to Ruby on Rails was driven by the unsustainability of their existing architecture. With over 80 microservices, adding new features was slow and required coordination between multiple teams. This complexity led to long delays, sometimes up to three months, to roll out new features. Switching to Rails allowed for faster development cycles and reduced the complexity of handling multiple services.

How did the team feel about transitioning to Ruby on Rails, given that they had no prior experience with it?

Initially, many team members, including John, were reluctant about making the switch to Ruby on Rails, especially since they had no prior experience with it. However, once they started using it, the response was positive, and they found that it offered a forgiving environment that allowed them to learn and adapt quickly. The transition was challenging but ultimately rewarding.

What role did Freedom play in the decision to move to Ruby on Rails?

Freedom was the key advocate for the switch to Ruby on Rails. He recognized the limitations and inefficiencies of the existing Java-based microservices system, particularly how adding new features required collaboration across multiple teams and services. His vision for a more streamlined and efficient system was what ultimately led to the migration to Rails.

What were some of the challenges Flexar faced during the migration to Ruby on Rails?

One of the main challenges Flexar faced during the migration was ensuring that their existing systems and features continued to function during the transition. Additionally, the team had to quickly learn Ruby and Rails while still maintaining the company's operations. The process was intensive, and there were a few months of fixing bugs before the system was fully stable.

How long did the migration from Java to Ruby on Rails take, and was the initial timeline met?

The migration initially had a three-month deadline set by Freedom, but the team ended up completing the process in four months. Despite some initial delays, they successfully launched the new Rails-based system with a working application, though there were a few weeks of post-launch bug fixing.

What surprised John about working with Ruby on Rails, especially coming from a front-end background?

John was surprised by how quickly the team adapted to Ruby on Rails, especially given the short learning curve. Despite having little prior experience with Rails, the team was able to produce functional code within a few months and even improved their work as they learned more. He was also surprised by how flexible and forgiving the framework was, especially when their code was not perfect initially.

What is the community like in the Ruby on Rails ecosystem, according to John?

John found the Ruby on Rails community to be incredibly welcoming and inclusive. He was initially skeptical about the claims of a supportive community but found that it lived up to the hype when he attended RailsConf. He appreciated the openness and friendliness of the people he met, making it easy to interact and collaborate with others in the ecosystem.

How did the launch of Flexar's new Rails app coincide with RailsConf, and what impact did that have?

The timing of Flexar's app launch at RailsConf was coincidental but serendipitous. During Arena Nazerova's keynote, Flexar was mentioned as a case study, which provided a significant boost to the team's morale. The community's support during the conference, especially after hearing about Flexar's transition to Rails, made the team feel motivated to go ahead with the launch, despite some of the challenges they were facing.

What role did Freedom's leadership style play in the successful migration to Ruby on Rails?

Freedom's leadership style was pivotal to the success of the migration. He made decisive moves and led the team with a clear vision. He was not in favor of a gradual approach but instead pushed for an all-in commitment to the new system. This confidence and commitment to going all in helped guide the team through the challenging transition and ensured they stayed focused on the goal.

How does John feel about continuing to work with Ruby on Rails in the future?

John is enthusiastic about continuing to work with Ruby on Rails. He believes it is a great tool for startups or companies facing scalability challenges. He values its simplicity and speed, which can eliminate some of the complex engineering discussions that slow down development. John sees Rails as an important part of his development toolkit and is eager to keep using it moving forward.