What is this series?

In 2025, I led one of the most challenging and rewarding projects of my career at Billie: modernising a mission-critical workflow involved in the real-time risk assessment process.

Over the years, as Billie’s product and operations evolved, the technical landscape supporting these decisions naturally grew more complex. To keep scaling effectively, we needed a fresher, more flexible architecture - one that improved autonomy, made change easier, and positioned us well for future growth.

This series is a reflection on how we approached that journey. I’ll share the architectural principles that shaped our redesign, key decisions we made along the way, how we carried out a “zero-downtime” migration, and the personal lessons learned from planning and delivering a project of this scale.

Table of contents

• The smart consumer: when once good architecture becomes a bottleneck
• The blueprint: designing the orchestrator
• Changing the engine at 100 MPH: steps and strategies for minimising downtime
• A retrospective: results, mistakes, lessons & future plans