H. Rosenberg Consulting

Project Portfolio

A showcase of key projects and contributions across various industries, demonstrating expertise in Java and modern software development.

UNI - Next generation card payment solutions
Nets | September 2020 - December 2024

As a Senior Java Developer, I was instrumental in developing and optimizing the real-time transaction validation and routing system for Nets' acquiring side. This critical system, serving as a high-performance intermediary between authorization and clearing, handles crucial validations for merchant, PSP, acquirer, card recognition, routing, and risk, all under stringent latency requirements for real-time authorizations and high-volume batch processing for clearing transactions.

Role:

Senior Java Developer

Technical Details:

The core challenge was to achieve sub-millisecond lookup times for critical data (e.g., 200,000 merchant records, 1 million scheme account ranges) under high transaction loads. Initial attempts with MongoDB, even in a real-time OpenShift cluster, proved insufficient for the strict performance demands. The solution engineered involved an in-memory data store for these critical registers, populated by consuming compacted Kafka topics. This approach, while introducing a startup delay for data ingestion, enabled the necessary low-latency lookups. Robustness and 24/7 availability were ensured through multiple instances and the use of deduplicating data structures, particularly for the large scheme account range dataset, to optimize memory usage and lookup efficiency.

Key Technologies:

JavaKafkaMongoDBOpenShiftIn-memory Data Structures
Telecom software stack
CallMe | 2010 - 2017

Architected and Lead developer for the Java Stack including: Shop gateway, Credit Check, Product integration ( e-tray, MS365, Matas, SAS ), Number management, Warranty, Prepaid subscription, Sim-swap, CPR for address updates, Usage and Online invoices

Role:

Senior Software Engineer

Technical Details:

Key Technologies:

JavaSpring BootSpring-CloudSpring BatchSOAPTomcatOracle DBApache CamelJUnitMockitoDocker