Composable Architecture: A Practical Example

[fjaviergar07]

Several blogs already explain composable architecture, like this one, or this well-summarized explanation from @stevang.

Composable architecture can ultimately lead to MACH architecture, also covered by @MichalKrawczyk  in this blog.

But if you haven’t read these articles, you might have heard the usual analogy with LEGO bricks, which you can combine to solve endless business challenges.

In this blog, I won’t provide a step-by-step tutorial, but I will showcase how to bring composable architecture to life through a practical example.

Example Scenario: Cost Center Data Transfer

Let’s imagine you need to send Cost Center master data from S/4HANA to SuccessFactors—simple as that.

The first step would be to check the SAP Business Accelerator Hub. By filtering for one of these systems and searching under integrations, you’ll find an integration package designed for this purpose: Replicate Cost Centers from SAP ERP or SAP S/4HANA to SAP SuccessFactors Employee Central (link).

Business Accelerator Hub - Standard iFlow

That could have been the end of our task. But upon opening the documentation, we encounter an important warning:

"Caution: If you set up a new integration and plan to move from SAP ERP to SAP S/4HANA, we recommend using the SAP SuccessFactors Employee Central integration with SAP Master Data Integration to replicate cost centers from SAP S/4HANA (on-premise edition) or SAP S/4HANA Cloud Private Edition to Employee Central. For more information, refer to Scenario: Integrating Cost Center from SAP Master Data Integration to Employee Central."

It goes on to warn that the ODTFINCC software component will be deprecated with the SAP S/4HANA 2025 release, urging a transition to SAP Master Data Integration.

How Composable Architecture Helps

We don’t want to rely on an integration package that will become obsolete with a future upgrade. But what if we don’t have SAP Master Data Integration? Here’s where composable architecture can help us.

Exploring further in the SAP Business Accelerator Hub, we find building blocks that meet the requirement. For instance, we can leverage the standard SAP event for Cost Centers (link) and the Cost Center API (link) in S/4HANA. For SuccessFactors, we can draw inspiration from the standard iFlow mentioned earlier, which uses the FOCostCenter Object over the OData v2 API (link).

S/4 Cost Center Event

S/4 Cost Center API

SFSF FO API - Cost Center Entity

 By orchestrating these building blocks using the Cloud Integration capability of Integration Suite and Advanced Event Mesh, we can create a solution that looks something like this:

Custom iFlow joining the standard SAP components

Integration Flow Overview:

1. Event Consumption: Capture the Cost Center event and extract relevant details like Cost Center ID.
2. API Call to S/4 HANA: Use a GET operation on the API to retrieve the full content. In this case, instead of calling the backend API directly, we use an API Proxy exposed in the Developer Hub for further reusability.
3. Transformation and call to SuccessFactors: Map the API response to the payload needed for SuccessFactors. Here, I reused the structure and even a Groovy script (tweaked a little bit) from the SAP package to build the final payload.

While some initial work was needed to “enable” the API and events for this use case (I call it planting the seeds), future applications can use the same events and APIs with minimal configuration—what I’d call harvesting.

This is the beauty of composable architecture: not in the first implementation, but in the second, third, and beyond, when it can accelerate new integrations.

Final Thoughts

Returning to the LEGO analogy, to start building with these blocks, you’ll need to first acquire some, right?

Some, like Integration Suite or Advanced Event Mesh and other BTP services, do need to be purchased. But other blocks, such as events and APIs, are available as commodities. Your system just needs to be prepared for them. If you’re on S/4HANA Cloud, you’ll have access to most of these resources. For on-premise systems, the more up-to-date you are, the more building blocks you’ll have at your disposal.

From this perspective, SAP’s sales pitch to stay on the latest S/4HANA version or move to S/4HANA Cloud to enhance your ability to respond quickly to real-world challenges has a valid point. For instance, the Cost Center API has been available since the 2020 FPS02 release. If you’re on an older S/4 version or ECC, you won’t have it, and same applies for the events. While you can create your own events or APIs in older versions (link) (link), you miss out on the advantage of having these “LEGOs” out of the box.

And of course, if you want to adapt your events and APIs without impacting future upgrades to have your customized LEGO bricks and show off in front of other kids, you can do it with RAP, but only starting on S/4HANA 2022.

I look forward to hearing your thoughts in the comments!

Javier