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Spotlight on Data: Refactoring a Million-Line Codebase with Maude Lemaire

An interactive case study from Slack

Maude Lemaire

In late 2017, Slack's largest customers were plagued with relentless performance-related outages, due in part to the fact that public channels, private channels, and DMs were stored in completely distinct ways. Instead of shipping scrappy, short-term fixes, the company opted to address the root problem and completely refactor problematic functionality by consolidating any redundant database schemas.

In this edition of Spotlight on Data, Maude Lemaire explains how Slack succeeded by mapping out a precise plan that was careful to scope the effort to only its necessary components. Join in to learn real-world, successful techniques for modernizing your infrastructure from the ground up—live and in production. You’ll discover how to properly assess the risks associated with a large refactoring effort; convince leadership that the intimidating, months-long rewrite is worth it; document the complex process for teammates and leaders alike; and prepare for the unexpected, all while staying optimistic.

O’Reilly Spotlight explores emerging business and technology topics and ideas through a series of one-hour interactive events. You’ll engage in a live conversation with experts, sharing your questions and ideas while hearing their unique perspectives, insights, fears, and predictions for the future.

In every edition of Spotlight on Data, you’ll learn about, discuss, and debate the tools, techniques, questions, and quandaries in the world of data. You’ll discover how successful companies leverage data effectively and how you can follow their lead to transform your organization and prepare for the Next Economy.

What you'll learn-and how you can apply it

By the end of this live show, you’ll better understand:

  • How to properly assess the risks associated with a large refactoring effort
  • Strategies for convincing leadership to invest in a large-scale refactoring effort
  • How to effectively document your refactoring process

This training course is for you because...

  • You're a developer or software architect who needs to overcome technical debt by refactoring large-scale, highly visible services.


  • Come with your questions for Maude Lemaire
  • Have a pen and paper handy to capture notes, insights, and inspiration

Recommended follow-up:

About your instructor

  • Maude Lemaire is a San Francisco-based staff engineer at Slack, where she’s actively working to boost developer productivity. Maude spends most of her time refactoring unwieldy chunks of code, consolidating redundant database schemas, and documenting everything in between.


The timeframes are only estimates and may vary according to how the class is progressing

Monday, November 18, 2019, at 10:00am PT / 1:00pm ET

  • Introduction and presentation (15 minutes)
  • Interactive discussion and Q&A (45 minutes)