Side-by-Side Extension involves building separate applications outside the core SAP system, often on the SAP Business Technology Platform (SAP BTP).

Where it runs:

• On SAP BTP or any external cloud platform
• Communicates with SAP S/4HANA via APIs (ODATA, REST, BAPI, etc.)

 Typical Use Cases:

• Creating new apps without changing the core
• Complex integrations with third-party systems
• Mobile apps or web portals
• Machine learning or advanced analytics scenarios

 Pros:

• Decoupled from core = less impact on upgrades
• Greater flexibility with tools and languages (e.g., Java, Node.js, Python)
• Scalable and cloud-native development
• Ideal for innovation scenarios

 Cons:

• Requires setting up integration (APIs, authentication, etc.)
• Potential latency (depending on use case)
• Higher architectural complexity