Behind the Fizzy Infrastructure with Kevin McConnell

In this episode of RECORDABLES, we dive into the infrastructure journey behind Fizzy. Lead Programmer Kevin McConnell walks through the ambitious plan to give every customer their own SQLite database and the challenges the team ran into along the way. What started as a unique way to support both self-hosted and SaaS models evolved into a performance experiment, pushing multi-tenant design further than we had before.

But as launch day approached, the tradeoffs became harder to ignore. Kevin shares what worked, what got complicated, and the pivotal decision — days before release — to unwind months of work and revert to a more conventional setup. This conversation is a candid look at architectural bets, emotional attachment to big ideas, and knowing when to change course.

*Timestamps*

00:00:00 – Introduction
00:02:56 — The Fizzy bet: one SQLite database per customer
00:06:57 — The challenge with SQLite and global writes
00:14:35 — Switching to MySQL (and fixing the fallout)
00:18:55 — Why the Apartment gem wasn’t enough
00:22:55 — Live Demo: Making Writebook multi-tenanted in minutes
00:31:36 — Built-in safety checks to prevent data leaks
00:35:17 — Replication, failover & “emergent behavior”
00:43:28 — What’s Next: upstreaming to Rails and future plans

*Links*

Mike Dalessio’s Rails World 2025 talk: Multi-Tenant Rails: Everybody Gets a Database – https://www.youtube.com/watch?v=Sc4FJ0EZTAg

For the full episode transcript, visit https://dev.37signals.com/