After its founding 15 years ago, Tam Tam has encountered the limits of legacy systems used for the internal processes in recent years. To overcome these limits, multiple efforts have been made to enforce a transition to specific Enterprise Application Integration styles. Although the efforts resulted in working application interactions, the desire for an organized whole sustained. The motivation for this thesis project was to make one final effort towards a new architecture by providing a carte blanche for all steps to be taken as well as their outcomes. The main goal of this thesis project was to research the most logical „next step? for Tam Tam to take with the internal systems architecture and to derive which improvements this step brings into the picture. To reach this goal, a crossroad of three key elements is identified. 1. Context, the first element is to figure out what the current architectural landscape looks like and what can be learned from the previous attempts at integrating the systems. 2. Theory, the second element is to figure out how architectures can be compared, what the possible solutions are and which of those fits Tam Tam best. 3. Practice, the third element is to link the theoretical design to the practice to assess its feasibility, to evaluate which improvements for Tam Tam are introduced and, finally, to evaluate the chosen methodology. The choice for sub-steps in the chosen methodology is based on best practices and guidelines from available (relevant) literature and is adapted to be used in this specific context. The focus of this adaption is that the chosen steps must be adaptable to other contexts too. After the complete methodology has been carried out, the key deliverables can be divided into two different categories: science and Tam Tam. For science the main deliverables are: 1. An aggregated list of re-usable insights 2. A case study for an Enterprise Service Bus transition 3. Are-usable step-by-step approach from legacy systems architecture towards the „most logical? next architecture. The key deliverables for Tam Tam entail: A. A conclusion of the continuous effort towards Enterprise Application Integration B. Sellable BizTalk know-how C. An improved internal architecture with regard to flexibility, maintainability and adaptability Concluding, the given carte blanche allowed for a successful path towards the best fitting Enterprise Application Integration style for Tam Tam. Furthermore, the methodology used is assembled in such a way it can withstand usage in other contexts and can be seen as a first step towards a formal definition of said methodology. This re- usability is introduced by the context-free focus during the definition of said methodology.