Last year, Flexcar migrated its entire platform from a complex Java-based microservice architecture to a Ruby on Rails monolith. That shift happened almost in real time at RailsConf 2024, after Irina Nazarova announced it during her keynote.

One year later, Flexcar’s Director of Engineering, John Dewsnap, is joining us at RailsConf 2025 to share the full story of what happened before and after that launch.

RailsConf 2025 Keynote: “365 Days Later”

John’s keynote will explore how and why Flexcar left behind its 80 microservices in favor of a single Rails application.

At the time, switching to Rails was a radical decision. With the exception of CTO Freedom Dumlao, the team had no prior Ruby or Rails experience. But they reached a breaking point with their previous architecture when a caching layer had to be built to fetch car data that should have been readily available.

“It had to go out and make seven or eight different calls to get the data we needed and then present that to our front end," says John. "It literally is the bazooka to kill a mosquito analogy.”

After that moment, Freedom began exploring alternatives. Rails offered a chance to simplify the architecture, improve delivery speed, and cut down internal friction.

“We were definitely, I think as a group, reluctant,” John says of the early days. “I’m more of a frontend guy myself, so my big question was, how much are we changing the frontend?”

Ultimately, they kept React for their consumer-facing app and introduced Stimulus and Turbo internally. But everything behind the curtain was new.

And despite the steep learning curve, the transition moved fast. The team was able to migrate the entire product to Rails in just four months, with everyone adapting much faster than expected.

“Rails was very forgiving for us," says John. "We were writing not-the-best code at first, and some of it looked like Java, but it performed. Rails just dealt with it, which gave us the space to learn and improve. People felt comfortable fast, and by the end, they already wanted to go back and rewrite things better.”

Finding Community at RailsConf

Inspired by the enthusiasm in the room during Irina's keynote at RailsConf Detroit, the Flexcar team made a game-time decision to begin their migration to Rails that night. By noon the next day, the app was fully operational and taking real customer orders.

As John reflects back, he remembers this as one of the most exciting moments of his career. “Everyone was coming up to us like, How did it go? They cared and were hoping it went well. And we could say yes, we launched, it’s working, it’s running.”

“The community is the thing that stuck out," John says of his time at RailsConf 2024, which was his first Ruby or Rails conference. "There are tons of smart people. I went to tons of great talks. But the thing that stuck with me was just how accepting, nice, and open a community it is. In my 20-plus years in [the tech] industry, I’ve never had that before.”

What You’ll Take Away

John’s keynote will focus primarily on what happened after Flexcar's switch to Rails, including major changes in velocity, morale, and culture that extended beyond the engineering and product teams.

Attendees can expect to take away:

  • A real-world case study on transitioning from Java microservices to a Rails monolith
  • Honest insight into adopting Rails as a team with no prior experience
  • Lessons in managing change across engineering, product, and executive teams
  • A reflection on what Rails made possible for Flexcar’s product and people
  • And much more...

RailsConf 2025 tickets are on sale now. Join us in Philadelphia this July to hear John’s full story!

You can also watch our interview with John on the Ruby Central YouTube channel: