- Applies to
- SAP S/4HANA, SAP BTP
- Topics
- Clean core, extensibility, CAP, SAP Build
- Audience
- Architects and program leads
The problem
Every S/4HANA program faces the same daily question: a business team needs something the standard does not do. Building it the old way inside the ERP makes every future upgrade harder. Building everything outside adds integration and cost. The answer is to choose the right place each time.
The three options
- Key user extensibility: custom fields, simple logic and adapted screens using built-in tools. Best for small changes close to standard processes.
- Developer extensibility in the ERP: code that runs inside S/4HANA using released, upgrade-stable APIs only. Best when logic needs direct, fast access to ERP data within one transaction.
- Side-by-side on SAP BTP: separate applications, often built with CAP or SAP Build, that use ERP data through APIs and events. Best for new user experiences, cross-system processes and anything with its own lifecycle.
Five questions to decide
- Does it need to run inside the same transaction as the ERP posting? If yes, stay in the ERP with released APIs.
- Does it combine data from several systems? If yes, go side-by-side on BTP.
- Will it change often, or be used by people outside the ERP? Side-by-side is easier to evolve.
- Is it a field or a simple rule? Key user extensibility is usually enough.
- Does a standard API or event already provide the data? If not, plan that integration first.
Result
Each extension lands where it is cheapest to run and safest to upgrade, and your S/4HANA core stays close to standard for every future release.