This upcoming talk by Steven Zelaznik is a joint event hosted by Prairie Postgres and RubyChicago.

The Multi-Terabyte Trust Exercise: Validating Massive Postgres Migrations
Moving a self-hosted Postgres instance to a managed service like Azure is more than a data transfer—it’s a high-stakes mission where “spot-checking” simply won’t cut it. When downtime is limited and a risk-averse client demands absolute proof of data integrity, you can’t rely on luck.

This talk tells the story of migrating a multi-terabyte database with millions of rows by building a custom, Ruby-orchestrated validation framework. We’ll move beyond simple row counts to explore how we used pgcrypto, custom aggregate functions, and information_schema introspection to generate cryptographic proof that every byte arrived safely. We’ll also dive into the “Third Act Twists”—from the hidden time-tax of generated columns to the “string paradox” of JSON and binary data—and why a successful migration is actually won during the dry run.

The conventional wisdom is that database features are hard to test. That might be true when it comes to performance issues. It’s not the case when it comes to business logic and data integrity.
With the flexibility of Rspec custom matchers we can write database tests in the same style as the Thoughtbot shoulda-matchers.

For the non-Rubyists, the principles of writing these tests apply to any language.

• In person attendees MUST Register/RSVP with your First + Last name
• For folks who would rather not have their Meetup Display name be first + last name OR for folks who do NOT have a meetup account. Please RSVP via this form (https://forms.gle/oKbX26tQXDNBhBdH6 )
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• Note: Our host location also requires us to send a list of attendees ahead of time to get them registered with building security, so please update your Meetup name to your first + last name. (If not comfortable with doing so, feel free to DM Michelle on meetup.com or email [michelle@zooniverse.org](mailto:michelle@zooniverse.org) and title the email ‘October 2026 ChicagoRuby Meetup’ with your First + Last name or your First + email so that you can get registered with building security for the event.)

For remote attendance: Join us via the following Zoom URL.