"Clean Core" and SAP BTP: a secure path to upgrading your ERP

SAP ERP systems have always been famous for their high flexibility: businesses could tailor even the most complex processes to their specific needs. Naturally, all successful companies have their own unique requirements and adapt their ERP systems to suit their processes. Historically, companies have actively taken advantage of this opportunity, deeply adapting the system core to their specific needs. But over time, the system becomes so overloaded with unique custom developments that any change or update turns into a large-scale and risky project. Customization results in hundreds of Z-programs, standard table modifications and complex dependencies. As a result, the system becomes similar to a building with modified load-bearing walls. This reconstruction solves business problems. For a time... However, even the smallest update triggers unpredictable errors throughout the system.
This phenomenon is known as “technical debt”. Today, the ability to upgrade an ERP system quickly has become critically important, and not just for the sake of a new release. With every upgrade, SAP adds features that directly impact efficiency: new functions for production and financial management, industry standard support, enhanced localization (including Ukrainian) and new APIs for integrations. At the same time, the system is enriched with modern tools – for example, the built-in AI copilot SAP Joule and advanced analytics. If your system is “locked in” with legacy custom code, you simply won’t be able to adopt these enhancements. You will be left behind in terms of innovation, falling behind your competitors in your ability to adapt to new market conditions.
To understand the scale of the innovations, one needs only look at the current SAP S/4HANA development roadmap. The system is constantly expanding in key modules: tools for manufacturing engineering and logistics are being enhanced, centralized procurement and sales are being improved, and product compliance controls are being strengthened. In addition, industry-specific solutions are being added – ranging from commercial real estate management to specific secondary distribution chains. All these business innovations, together with modern automation tools, are becoming available only to those companies whose core systems are ready for regular updates.
SAP promotes the solution to this problem as standard – the Clean Core concept. It offers an evolutionary approach in which your standard ERP system remains unchanged. The system operates strictly according to SAP best practices, basic processes and simple configurations are safely executed within the system using standardized in-app extensibility, and complex, unique business logic is integrated externally via the SAP Business Technology Platform (BTP) cloud platform.
Because the core of the system remains unmodified, every SAP update goes smoothly and without the risk of disrupting company operations. Furthermore, you gain access to the latest tools, including artificial intelligence. In addition, SAP BTP operates as a complete all-in-one ecosystem offering a wide range of services. Businesses no longer need to allocate extra budgets for additional infrastructure: from database creation and backend configuration to hosting and application deployment – everything is implemented within a single platform.

Clean Core: Benefits for Business, IT, and Users

The transition to Clean Core is not just an IT project; it is a business transformation that changes operations on three levels:

Paths to Safe Extensibility: In-app and Side-by-side 

Keeping a Clean Core does not mean a complete ban on changes inside the ERP. The official cloud extensibility model offers a clear distinction: 
● In-app key user extensibility. Business experts can independently adapt UIs, add new fields or create reports directly in the system using low-code/no-code tools. Such changes do not affect the core.
● On-stack developer extensibility. Developers write code directly on the SAP S/4HANA stack. This is used for more complex tasks requiring close integration with SAP data (e.g., intensive SQL queries). The main rule is the use of only authorized public SAP APIs.
● Side-by-side extensibility. When it comes to loosely coupled applications, unique customer portals, or solutions that integrate with several systems at once, development is moved entirely to the SAP BTP cloud environment.

The other side of the coin 

Moving development to SAP BTP is a powerful and strategically correct step, but we must openly discuss the challenges the businesses need to be prepared for:

How does this work in practice? 

If safe in-app tools (Key User Extensibility) are enough to add a new dictionary field or tweak the interface, the approach for large-scale processes is entirely different. For example, a client needs a new, highly specific process for managing changes to customer records. This process required gathering data from various departments, multi-level management approvals, the automatic generation of complex PDF forms for electronic archive, and user-friendly dynamic UI screens for data entry. Previously, developers would inevitably have “hard-coded” this logic directly into the ERP. Today, it can be done differently by building a transparent side-by-side extension architecture.

● Interface: Using SAP BTP development tools, a modern transactional SAP Fiori app is created, providing a personalized user interface.
● Logic: All custom business logic (approvals, validations, document generation) is implemented directly in the cloud – within the SAP BTP ABAP Environment.
● Integration: This external application communicates with the core system (S/4HANA or CX) exclusively via standard business APIs (OData), using SAP BTP integration services (e.g., Destination Service). ● System Core: The ERP provides source data via APIs and receives the processed result.
After implementation, everyone wins: the business gets a custom-tailored tool covering its unique needs, there is standard integration monitoring, and most importantly – the system core remains completely clean and ready for any system updates.