Description
LG CNS, the IT services arm of LG Group, collaborated with Claude Code to modernize a 20-year-old enterprise system. With approximately 7,000 employees and $4.2 billion in 2025 revenue, LG CNS has been a leader in building mission-critical systems for over 35 years. Claude Code powered LG CNS's Build Factory, a turn-key software development service designed to modernize legacy systems at scale.
The project involved converting 2,888 of 2,913 APIs from a legacy system, achieving a 99.1% completion rate. The migration was completed in seven months at roughly 50% of the cost of a conventional rebuild. LG CNS also migrated 1,340 screens from a proprietary frontend platform to React, with backend and frontend conversions running simultaneously on 24/7 parallel tracks.
Claude Code was adopted as the standard development approach across LG CNS's 200-engineer Build Center. This enabled modernizations that were previously deferred due to cost, risk, and specialist shortages. The solution involved using Claude Code's agentic coding tool, which understands codebases, edits files, and helps ship faster. The tool was accessed through Amazon Bedrock, allowing LG CNS to run Claude within AWS security configurations.
The engineering orchestration layer built around Claude Code included legacy analysis, business logic extraction, code generation, testing, verification, and quality management. Projects were executed in pods of five to seven people, with tasks decomposed into small, clearly scoped tasks defined in YAML. Claude Opus 4.6 was used for core work, including architecture design and complex code generation.
The approach was validated on a real customer system, delivering a next-generation rebuild at half the conventional cost. The project went live in June 2026, with significant ROI achieved by making previously difficult projects possible. LG CNS plans to further develop the Build Factory into a rigorous modernization discipline, enhancing deterministic validation and automated quality measurement.
Key Takeaways
99.1% API conversion rate
50% cost reduction
1,340 screens migrated to React
24/7 parallel-track operations
Standard development approach
Agentic coding tool
AWS security integration
Engineering orchestration layer
Task decomposition in YAML
Claude Opus 4.6 for core work
What This Case Study Demonstrates
- Legacy system modernization
- Cost-effective migration
- API conversion
- Frontend migration
- Enterprise-scale projects
