Leander Vanderbijl - Modernising in Healthcare: A Case Study in Decision Making - DDD Europe 2025

Why It Matters

The migration shows how healthcare software providers can safeguard revenue and future‑proof their platforms by combining short‑term lift‑and‑shift with strategic cloud‑native redesign, a model increasingly vital as providers demand secure, scalable SaaS solutions.

Key Takeaways

• Legacy on‑premise system migrated via lift‑and‑shift then rewrite.
• Dual risk: customer demand for cloud and departing lead developer.
• Decomposed monolith into domain‑focused sync and EMR mini‑services.
• Leveraged AWS event bus for scheduling, reducing custom infrastructure.
• Observability and standardized APIs improved maintainability and scalability.

Summary

Leander Vanderbijl presented a detailed case study of how Mog, a patient‑relationship‑management platform used by GPs, migrated its legacy on‑premise application to a cloud‑native architecture at DDD Europe 2025.

He highlighted the tangled legacy stack—PHP 5, Java, Delphi, SQLite and MSSQL—combined with 15 years of technical debt and a lack of clear service boundaries. Facing two critical risks—a customer‑driven demand for a cloud version and the imminent loss of the sole developer who knew most of the code—Mog evaluated a quick lift‑and‑shift to EC2 against a full cloud rewrite.

Vanderbijl used the “ugly duckling” metaphor, noting that with effort the legacy system could become a “beautiful swan.” He described decomposing the monolith into domain‑focused sync services, an independent EMR mini‑service, and an event‑bus‑driven scheduler, while retaining the existing PHP UI as a bridge.

The hybrid approach delivered an immediate cloud presence to retain customers and bought time for a six‑to‑nine‑month rewrite that eliminated the knowledge gap, standardized APIs, and introduced observability. The story underscores that healthcare SaaS firms must balance rapid delivery with architectural refactoring to sustain growth and compliance.

Original Description

Domain-Driven Design Europe 2025 - Organised by Aardling (https://aardling.eu/)

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Modern developers know about microservices, they know about cloud native software, they want to build new microservices in cloud native technologies using the latest patterns.

Unfortunately many of us have massive legacy applications with heaps of tech debt, badly defined modules and spaghetti messes of code.

How do you modernise a legacy application? What choices are you likely to face and what are some strategies for making good decisions?

At Livi we migrated a large, on-premise legacy application to the cloud.

In this talk, we look at the challenges we faced, the hurdles we overcame (and some we didn’t), and the thinking behind the choices we made throughout our journey.

We will look at how we leveraged api patterns to solve problems with complexity, modern frameworks to solve, or at least hide, legacy code and cloud-native technologies to provide security and observability across the entire application. We will also analyse some of the options we didn’t use, and discuss why.

About Leander Vanderbijl:

Leander is an engineer and architect that has worked across the entire stack and has been working at Kry/Livi for the past number of years. He has developed large enterprise applications, migrated cloud platforms, designed data query frameworks, architected integration systems and built lots and lots of APIs. Having worked in large enterprises, small companies and, most recently, in healthcare, he has built the monolith, torn it apart and then rebuilt it again.