Rails Multi-Tenancy with Mike Dalessio

In this episode of RECORDABLES, we dig into our ambitious goal of moving from a commingled database to separate SQLite databases for every Fizzy customer. Lead Programmer Mike Dalessio walks through what multi-tenancy actually means in practice, why Rails doesn’t make it easy, and how the open sourced Active Record Tenanted gem makes it more seamless.

During the conversation, Mike does a live demo showing what it takes to convert an existing Rails app to multi-tenanted and the safeguards built in to prevent accidental data leaks. You’ll also hear about the edge cases of globally replicated SQLite, and why we ended up launching Fizzy without it.

*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

Active Record Tenanted – https://github.com/basecamp/activerecord-tenanted

Fizzy code base – https://github.com/basecamp/fizzy

Apartment – https://github.com/rails-on-services/apartment

Writebook Multi-tenant code branch – https://github.com/basecamp/writebook/pull/389

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