Modernizing a $4T Transaction Engine with Agentic Swarms
How a Fortune 50 bank migrated 15 years of legacy Java to Go in 4 months.
The Challenge
Global FinCorp's core ledger was built on a 2008 Java EE stack. It was stable but stagnant. Feature velocity had dropped to near zero because every change required weeks of regression testing. The estimated cost to rewrite manually was $12M and 3 years, with high risk of failure.
The Solution
We deployed a custom 'Strangler Fig' Agent Swarm. Instead of a big bang rewrite, agents identified isolated domains within the monolith, generated equivalent Go microservices, and wrote comprehensive parity tests. Human engineers shifted from writing boilerplate to reviewing architectural patterns and approving PRs.
Tech Stack
The Impact
The migration was completed in 4 months. The new architecture allows for daily deployments instead of quarterly releases. More importantly, the engineering team was retrained on Go and distributed systems during the process, upgrading the workforce alongside the software.
"We didn't just get new code; we got a new engineering culture. The velocity we're seeing now was unimaginable a year ago."