Uploaded March 2026 | Updated September 2026, 2 weeks ago

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Can a technical migration actually break your engineering culture? Sophie Koonin (Staff Engineer & Web Lead at Monzo) pulls back the curtain on Monzo’s grueling two-year journey from Flow to TypeScript.

This isn't a talk about code - it's a tactical guide for senior engineers and architects on navigating the "bends in the road" that turn a simple refactor into an organizational marathon.

⏱️ Video Timestamps (For Navigation)
0:00 - The Deceptive "Straight Road" of Migrations
02:15 - Why Monzo Chose the "Wrong" Horse (Flow vs. TypeScript)
05:40 - Proving the Concept: Getting Initial Buy-In
08:22 - Documentation: The Key to Onboarding Mid-Migration
11:05 - Shared Load vs. Dedicated Teams: The Trade-offs
14:30 - Tooling as Your Best Friend: Automating the Grunt Work
18:15 - The Mid-Project Slump: How to Set Hard Deadlines
22:40 - When to Stop: The Case for Reducing Scope
26:10 - Guardrails, Rollbacks, and Shadow Mode Testing
31:50 - The Result: Was 2 Years of Work Worth It?
35:10 - Final Framework: Should You Even Start This Migration?

🔗 Transcript available on InfoQ: bit.ly/4uDXBh4

#SoftwareArchitecture #EngineeringManagement #TypeScript #Monzo #TechDebt #webdevelopment