What are the key architectural decision points early in a transformation roadmap?

Several foundational decisions shape everything that follows and are expensive to reverse once the program is underway, making them the critical early-stage focus for a senior architect.

1. Deployment model — on-premise, RISE with SAP (private cloud), or public cloud S/4HANA, each with different implications for customization flexibility and operational responsibility.
2. Clean Core baseline — how much existing customization must be remediated before migration, and how that shapes timeline and cost.
3. Extensibility strategy — establishing the in-app vs. side-by-side decision framework the program will follow consistently, rather than deciding ad hoc per requirement.
4. Data architecture — master data governance approach, especially for organizations with multiple legacy systems whose data must be harmonized.

Getting these early decisions wrong doesn't just cause rework — it can invalidate the business case and timeline the whole program was approved against, which is why they warrant disproportionate architectural attention relative to decisions made later in execution.