Financial Services•12 months

Financial Services Platform Migration from WebLogic to Spring Boot

Major Financial Institution

$450K

Annual Cost Savings

65%

Infrastructure Reduction

12x faster

Deployment Speed

20x faster

Startup Time

200+

EJBs Migrated

Production Incidents

The Challenge

A Fortune 500 financial institution was running a critical trading platform on WebLogic 10.3 with 200+ EJB 2.x components. Annual licensing costs exceeded $400K, and the technology stack was preventing cloud migration and attracting modern development talent. The platform processed millions of transactions daily and required 99.99% uptime. Any migration approach that risked downtime or data integrity was unacceptable. Additionally, the development team had deep institutional knowledge of the legacy codebase but limited Spring Boot experience. Key constraints: - Zero tolerance for production downtime - Cannot freeze feature development during migration - Must maintain regulatory compliance throughout transition - Need to reduce infrastructure costs by 60% within 18 months

Our Approach

The Solution

I implemented a phased Strangler Fig migration strategy over 12 months: **Phase 1: Assessment & Foundation (Months 1-2)** - Mapped all 200+ EJBs and their dependencies - Identified 15 leaf-node modules with minimal coupling - Created Spring Boot application skeleton with dual-write capability - Established CI/CD pipeline for Spring Boot services - Set up feature flags for gradual traffic migration **Phase 2: Pilot Migration (Months 3-4)** - Migrated user profile service (lowest risk, high value) - Built Spring Boot wrapper that delegated to existing EJB via RMI - Gradually moved business logic from EJB to Spring Data JPA - Implemented comprehensive integration tests - Achieved first production deployment with 10% traffic **Phase 3: Core Services Migration (Months 5-9)** - Migrated 8 core services using proven pattern - Implemented event-driven architecture for service communication - Replaced stateful session beans with Redis-backed sessions - Migrated authentication/authorization to Spring Security - Achieved 70% traffic on Spring Boot services **Phase 4: Final Migration & Decommissioning (Months 10-12)** - Migrated remaining services - Removed RMI dependencies - Decommissioned WebLogic application server - Deployed to Kubernetes on AWS EKS - Complete knowledge transfer to internal team

Outcomes

Results & Impact

Successfully migrated 200+ EJBs to Spring Boot microservices with zero production incidents

Eliminated $400K annual WebLogic licensing costs

Reduced deployment time from 3 hours to 15 minutes

Improved application startup time from 10 minutes to 30 seconds

Enabled cloud migration to AWS, reducing infrastructure costs by 65%

Development velocity increased 3x with modern tooling and frameworks

Successfully hired 5 new developers (previously struggled to find EJB talent)

Achieved 99.99% uptime maintained throughout entire migration

"The migration was executed flawlessly. We eliminated hundreds of thousands in licensing costs while improving developer productivity. Most importantly, we did it without any production incidents or business disruption."

VP of Engineering

Fortune 500 Financial Institution

Technology Stack

Before Migration

WebLogic 10.3

EJB 2.x

Stateful Session Beans

JMS

JNDI

Oracle 11g

After Migration

Spring Boot 3

Spring Data JPA

Spring Security

Redis

Kafka

PostgreSQL 14

Kubernetes

AWS EKS

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