CAST Highlight and CAST Imaging enabled AWS AML to develop a data-driven modernization roadmap for a .NET Payroll monolith, accelerating the shift to containerized, PaaS-ready services.

Challenge

Employment Hero’s payroll platform served 300,000+ businesses, but a monolithic .NET Framework codebase on Windows and SQL Server of 1.5+M lines of code, slowed releases and change management. A single background queue throttled workloads, risking delays during peak events.

With complex award rules and rapid growth, the team needed stronger resilience, faster delivery, and better cost control while readying the core “Pay Run” engine for sustainable modernization.

Solution

AWS AML asked CAST to baseline the current state and shape the modernization roadmap.

CAST Imaging mapped dependencies and transaction paths; CAST Highlight scored cloud readiness and risk. Insights showed how to decouple the monolith and prioritize the Pay Run engine, identifying service candidates, refactoring priorities, and risk hotspots – giving EH and AWS AML a plan to evolve .NET Payroll from IaaS toward managed PaaS and cloud-native services.

Results

With CAST’s data-driven insights and a clear modernization plan, Employment Hero accelerated outcomes rather than experimenting blindly. Teams focused work where it mattered, enabling 83% faster deployments and 85% faster builds.

Engineers reclaimed 4 hours each per week – adding up to 340 hours weekly – by removing analysis guesswork and rework.

The shared blueprint also reduced risk, improved coordination, and paved the way for selective PaaS adoption.