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.


Project Overview

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.


65%Time Saved
8MoROI Period
5K+Transactions/Sec
Replacing Legacy Mainframe Fraud Systems in 90 Days
The Challenge

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.

Data SilosManual ProcessLimited AccessTight Deadlines

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

Java
Spring Boot
PostgreSQL
AWS
Kafka
Docker
Kubernetes
Falcon
THE SOLUTION

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

Self-Service Analytics

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.

< 100ms latency

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

Final Outcome

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.

95%
Faster Processing
vs Mainframe
10K+
TPS Capacity
Transactions /Sec
3 Mo
Delivery Time
POC Delivered
$2M+
Annual Savings
Infrastructure Cost

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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