Hergy Fongue
Software Engineer at Finanz Informatik
Frankfurt am Main, Germany
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Hergy Fongue is a backend Developer at Finanz Informatik, the central IT service provider of the German Savings Banks Finance Group. He plays a key role in the transformation of the central data warehouse from mainframe-based infrastructure to a modern, decentralized architecture. His focus lies on building modern cloud-native core components for business-rule-driven data correction. This involves ensuring both the semantic integrity of data and the flexible processing of individual records as well as large files.
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From Mainframe to Modular: The Developer’s Guide to Legacy Modernization
Modernizing legacy systems is one of the toughest and most rewarding challenges in enterprise IT. hands-on lessons from transforming mission-critical mainframe and legacy systems into a modern banking platform serving 50 million customers of the German Sparkasse Finance Group.
From COBOL to Java, from monolithic mainframes to shared services and cloud-native architectures: we explore different modernization strategies and where the mainframe still makes sense today.
A special focus lies on empowering developers. By automating routine tasks, reducing friction in daily work, and improving the developer experience, teams are enabled to actively shape the future of the platform instead of just maintaining the past.
From Mainframe to Modular: The Developer’s Guide to Legacy Modernization
Die Modernisierung von Legacy-Systemen ist der entscheidende Enabler für datengetriebene und KI-basierte Banking-Plattformen der Zukunft. In ihrer Keynote zeigen Lars Reichert und Hergy Fongue von der Finanz Informatik, wie sie geschäftskritische Mainframe- und COBOL-Systeme für rund 50 Millionen Sparkassen-Kunden zu einer modernen, skalierbaren Plattform transformieren und damit Data Lakehouse und KI-Anwendungen erst möglich machen.
Anhand konkreter Architekturbeispiele führen sie vom monolithischen Mainframe zu dynamischen Services, generischen Konfigurationsservices und einer echten Multikanal-Architektur. Mit hands-on Beispielen aus der Praxis geben sie Einblick in moderne Code-Transition-Ansätze inklusive KI-Unterstützung.
Während die Modernisierung der IT für die meisten offensichtlich ist, wird häufig übersehen, dass auch die Struktur der Zusammenarbeit grundlegend neu gestaltet werden muss. Denn Organisationen bauen unweigerlich ihre eigenen Kommunikationsmuster in ihre Systeme ein: Wer mit wem spricht, wie oft und in welche Richtung Informationen fließen. Erst wenn auch die Teamstrukturen bewusst auf das Zielbild der modularen Architektur ausgerichtet sind und nicht mehr aus der alten Monolithen-Welt stammen, gelingt die Modernisierung nachhaltig. Lars und Hergy teilen ehrliche Learnings und konkrete Takeaways – praxisnah und direkt umsetzbar für alle, die selbst Legacy-Systeme modernisieren wollen.
From COBOL to Java: How Developers Transition 60 Years of Legacy into Modern Java Services
COBOL systems written decades ago still power some of the most critical parts of modern banking. But how do you modernize systems serving more than 50 million customers without disrupting daily operations?
In this workshop, we share our modernization journey within the German Sparkasse Finance Group, where mission-critical mainframe applications continue to process core banking workloads every day.
Faced with hundreds of interconnected COBOL programs, limited documentation, retired domain experts, and years of temporary solutions turned permanent features, we first had to answer a fundamental question: What does the system actually do?
Through concrete examples, we show how we reverse engineered business capabilities from legacy systems, analyzed data models and processing flows, identified the logic worth keeping, and deliberately discarded complexity that no longer created value.
You'll see how we transformed monolithic applications into modular services, introduced shared and configurable business capabilities, and designed a target architecture focused on maintainability, scalability, and developer productivity.
We also demonstrate how AI helped developers understand legacy code, uncover hidden dependencies, and accelerate modernization efforts.
Beyond technology, we explain how we used developer experience as a lever for transformation. By improving developer experience, automating repetitive tasks, and reducing friction in daily work, teams were able to focus on innovation instead of maintenance.
This workshop is for developers and architects facing large legacy environments and looking for practical strategies to modernize systems without simply rebuilding yesterday’s architecture with today’s technology.
WeAreDevelopers World Congress 2026 - Europe Sessionize Event Upcoming
JAX - From Mainframe to Modular: The Developer’s Guide to Legacy Modernization
The modernization of legacy systems is the key enabler for the data-driven and AI-based banking platforms of the future. In their keynote, Lars Reichert and Hergy Fongue from Finanz Informatik will demonstrate how they are transforming business-critical mainframe and COBOL systems for approximately 50 million savings bank customers into a modern, scalable platform, thereby enabling data lakehouse and AI applications.
Using concrete architectural examples, they will demonstrate the transition from a monolithic mainframe to dynamic services, generic configuration services, and a true multichannel architecture. With hands-on examples from real-world practice, they will provide insight into modern code transition approaches, including AI support.
While the need to modernize IT is obvious to most, it is often overlooked that the structure of collaboration must also be fundamentally redesigned. This is because organizations inevitably embed their own communication patterns into their systems: who speaks with whom, how often, and in which direction information flows. Only when team structures are consciously aligned with the vision of modular architecture—and no longer stem from the old monolithic world—can modernization succeed in the long term. Lars and Hergy share honest insights and concrete takeaways—practical and immediately actionable for anyone looking to modernize legacy systems themselves.
Hergy Fongue
Software Engineer at Finanz Informatik
Frankfurt am Main, Germany
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