Project 1: Multi-Tenant SaaS Platform: Data Integration & Pricing Management
New development of ELT pipeline (replacement for Java 6 legacy)
Integration of heterogeneous source systems (CSV, Excel, Email, external DBs)
Event-Sourcing for complete auditability
Multi-tenant architecture for tenant-capable data processing
Stakeholder workshops for requirements analysis
Event-driven architecture with Axon Framework and Apache Kafka
AWS services (EC2, S3, Lambda, SQS, API Gateway) for cloud integration
PostgreSQL with tenant-specific schemas for multi-tenant data isolation
REST API design with Spring Boot for external system integrations
Comprehensive testing strategy (JUnit, Spring Test, Postman, PACT, ArchUnit)
Achieved ELT performance improvement from 30+ min to 1–5 min
Saved 2–3 hours daily through workflow automation and 10–20 hours/week through event-sourcing auditability
Ensured 100% audit compliance and secure multi-tenant data isolation for 10+ tenants
Project 2: Multi-tenant CRM System Modernization
Migration of CRM system (20+ years PHP/MySQL) to Java microservices
Domain-Driven Design implementation and establishment of Test-Driven Development
Multi-tenant-capable SaaS architecture with tenant-specific databases
Comprehensive testing strategy (JUnit, Spring Test, Postman, PACT, ArchUnit)
REST API design with Spring Boot for cross-tenant integration
Kubernetes and Docker for container orchestration
Achieved 2× performance improvement and reduced deployment time from 40+ min to 5–7 min
Completed migration without production outages and delivered scalable multi-tenant solution for 15+ customer tenants
Project 1: Deutsche Bahn Mobile Backend
Designed backend for Android app serving 50,000+ DB employees
API design and microservices architecture using Domain-Driven Design
Broke down legacy monolith (2,000,000+ lines) into 7 microservices with bounded contexts
Developed Kotlin-based microservices with Apache Kafka
Optimized PostgreSQL database with indexes and partitioning for high availability
Designed REST API for mobile connectivity and utilized Kubernetes and Docker for orchestration
Achieved millisecond-range performance, zero-downtime migration, and 99.9% uptime
Project 2: Government Digitalization Portal
Fullstack development of internet portal for public administration with Java/Spring Boot backend and Angular frontend
Integrated various administrative backend systems via REST API gateways
Implemented secure-by-design microservices architecture and ensured 85% test coverage
Utilized Kubernetes, Docker, Helm, and Terraform for deployment and compliance with GDPR and BITV 2.0
Processed 100,000+ transactions/month with 24/7 high availability
Senior Java Developer with 5+ years of enterprise experience in rapidly modernizing complex legacy systems and building scalable cloud-native architectures. Specialist in Domain-Driven Design with proven ability to quickly understand new business domains and successfully migrate 15+ legacy services with an average 65% performance improvement.
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