Replacing Legacy Mainframe Fraud Systems in 90 Days
Modernizing mainframe systems for a large bank to enable real-time fraud detection using microservices architecture, reducing processing time from days to milliseconds.
Replacing Legacy Mainframe Fraud Systems in 90 Days
Modernizing mainframe systems for a large bank to enable real-time fraud detection using microservices architecture, reducing processing time from days to milliseconds.

Transforming Data Accessibility
The project had a predetermined timeline of three months, with the aim of developing a Proof Of Concept (POC) to replace the bank's mainframe with a modern microservices architecture. Edstem's responsibility was to provide two deliverables: a full solution design with architecture, and a working POC showcasing an end-to-end workflow for a selected transaction type. Several delays occurred due to access restrictions and onboarding to client systems. Development time was reduced to one month after consolidating all necessary details from client technical architects. Strict security policies further slowed setup of required tools and environments. The mainframe apps had been developed over several years, with limited documentation, making analysis difficult. Despite these challenges, Edstem delivered a full solution architecture and a working POC with all agreed components on time, overcoming obstacles like deployment access and individual service pipelines.
Decoding Legacy Systems Under Tight Deadlines
The mainframe applications were complex and heavily customized. Understanding the system, analyzing transaction flows, and designing a microservices replacement under tight timelines required a strategic approach and careful planning.
IMPACT
10K+
Users Empowered
Approach to Modernization
Edstem studied legacy mainframe apps and designed a scalable microservices architecture. Two architectural patterns were explored: Choreography and Orchestration. The final system adopted an orchestrator to manage synchronous workflows, connecting multiple services via REST APIs.
Technology Stack
Microservices-Based Architecture
To modernize the bank's mainframe systems, Edstem proposed a scalable, cloud-ready microservices design. Services were built with Java Spring Boot and communicated via message queues. Initially, the design used a Choreography pattern, but after client feedback, it was revised to an Orchestrator pattern to support synchronous workflow. Both versions were presented and well-received by the client's technical architects. The POC demonstrated a single transaction type from end to end. Transactions were read from input message queues as fixed-length messages, parsed into Java POJOs, enriched with additional data (mocked for POC scope), and transformed to Falcon's required format. The POC then sent transactions to Falcon scoring server via REST endpoints, throttled to 300 TPS. Failed transactions were stored in PostgreSQL for retry, and the Falcon response was processed to extract decision codes (Approve, Decline, Quarantine). Final output messages were written back to output queues. This solution proved the architecture’s feasibility and validated real-time fraud detection using microservices, message queues, and Falcon integration.
Self-Service Analytics
Empower every team member to access, analyze, and visualize data without technical expertise

Real-Time Updates
Transactions are processed in real time using Falcon scoring, with throughput throttling and retry handling to ensure reliability. This supports high-volume, synchronous transaction processing.
Enterprise Security
Bank-grade security with role-based access control and comprehensive audit trails
- SOC 2
- GDPR
Event-Driven Processing
Reliable ingestion and processing using message queues
Real-Time Scoring
Falcon fraud detection engine integration for instant transaction decisions
Secure Communication
REST API microservices with enterprise-grade security
Orchestrator Pattern
Centralized workflow management enabling synchronous transaction processing
Results That Matter
Despite multiple challenges, Edstem delivered the solution architecture and a working POC with all features on time. The client highly appreciated the solution. Modernizing legacy systems with microservices improved efficiency, scalability, and customer experience. The project demonstrates that careful planning, scalable solution design, and expertise in microservices are key to successful legacy modernization.
Before
- Legacy COBOL mainframe applications
- 3-5 days for system changes
- Limited scalability and high costs
- Difficult to maintain and update
After
- Modern microservices architecture
- Hours for deployment with CI/CD
- Horizontal scalability with Kubernetes
- Easy maintenance with Spring Boot
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