QCon AI New York 2025: Moving Mountains: Migrating Legacy Code in Weeks Instead of Years
Summary
At QCon AI New York 2025, David Stein, Principal AI Engineer at ServiceTitan, shared insights on efficient legacy code migration. He introduced the Principle of Acceleration and the Assembly Line Pattern, proving that migrations can be streamlined significantly.
Key Insights
What is the "Assembly Line Pattern" David Stein describes and how does it speed up legacy migrations?
The Assembly Line Pattern is a sequential, automated workflow for breaking a large migration into repeatable, validated steps — Decompose, Standardize, and Automate — that let teams convert, test and deploy migration “pebbles” instead of attempting a single big rewrite; by treating migration tasks as an assembly line (objective → plan → code → test → release) and adding automated validation (a "physics engine") plus agents to run tasks, ServiceTitan shortened what used to take quarters or years into a number of weeks according to Stein's talk at QCon AI New York 2025[1].
Sources:
[1]
What does Stein mean by the "Principle of Acceleration" and is data or business logic risk reduced by this approach?
The Principle of Acceleration, as presented by Stein, emphasizes speeding the migration cadence by decomposing large changes into small, validated units and automating their delivery so teams gain confidence and iterate quickly; this reduces time-at-risk because smaller, tested increments are easier to validate and roll forward, though Stein's case study notes migrations still require careful planning around production data, complex SQL/C# logic, and metric validation to avoid functional regressions[1].
Sources:
[1]