Henning Schwentner - DDD for Mergers and Acquisitions - DDD Europe 2025

Why It Matters

Understanding and modeling process differences before system consolidation prevents costly integration failures and unlocks the true synergies of mergers and acquisitions.

Key Takeaways

• Collaborative modeling reveals hidden process differences in M&A integrations.
• Parallel systems often fail to deliver synergies after acquisitions.
• Scope dimensions—granularity, time, domain purity—guide modeling depth effectively.
• Modularizing legacy monoliths enables selective system combination, not full replacement.
• Domain‑Driven Transformation offers strategic, tactical, organizational fixes for legacy debt.

Summary

Henning Schwentner opened his talk with a tongue‑in‑cheek love story, then pivoted to the real challenge: integrating two legacy leasing platforms after a merger. He framed the problem as a choice between keeping both monolithic systems in parallel or consolidating into a single solution, warning that either extreme can erode expected synergies. He introduced collaborative modeling—event storming, domain storytelling, and other lightweight workshops—as the means to surface hidden process variations between the acquiring firm (Alhorn) and the target (Cosmo). By applying three scope dimensions—granularity, point‑in‑time, and domain purity—teams can decide how detailed a model should be, whether to map current or future processes, and whether to focus on business logic or its digital implementation. Schwentner illustrated these concepts with a step‑by‑step comparison of the leasing workflow, moving from a high‑level "cloud" view down to the "kite" level where divergences appear, such as contract signing steps. He argued that outright system replacement is rarely viable; instead, modularizing and modernizing each monolith, then recombining the best bounded contexts, yields a more sustainable architecture. This approach, he called Domain‑Driven Transformation, tackles strategic (big‑ball‑of‑mud), tactical (poor domain expression), and organizational (team structure) ailments. The takeaway for executives and architects is clear: use collaborative, scoped modeling to diagnose integration gaps, then apply domain‑driven modularization rather than a blunt data migration. This reduces risk, preserves valuable legacy functionality, and accelerates value capture from M&A activity.

Original Description

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

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In todays business world, companies merge for various reasons. Most of the time, these companies have software systems in place that have more or less the same functionality and shall be merged, too. In this talk we look at how the different tools from the DDD toolbox can help us doing the transition.

About Henning Schwentner:

Coder, Coach, Consultant at WPS – Workplace Solutions

Henning loves programming in high quality. He lives this passion as coder, coach, and consultant at WPS – Workplace Solutions. There he helps teams to structure their monoliths or to build new systems from the beginning with a sustainable architecture. Microservices or self-contained systems are often the result. Henning is author of “Domain Storytelling” (Addison-Wesley 2022), “Domain-Driven Transformation” (Addison-Wesley 2024) and the www.LeasingNinja.io.