Enterprise Architecture and Domain Driven Design – Build Custom Business Logic as Microservice or part of the COTS Application?

As enterprise Architects, depending on the organization we are adopting readymade software applications (or COTS) and tailoring or customization of the software to the needs of the organization. The tailoring can involve UI changes, workflows changes, integrations with other systems in the organization and sometimes business logic added or modified. The UI changes usually must happen on the COTS (Component of the Shelf) application and so are workflows unless you are building a UI façade for this application. I saw one organization did build a completely different Web App to provide its employees access to work shift schedules as the Time and Attendance system could not handle the access by the hundreds of thousands of employees and save on licensing and infrastructure costs. This leaves us with Integrations and business logic. In this installment. I will address Business Logic.

Should we build the custom Business Logic as Microservice or part of the COTS Application?

Aha, this is a tough decision. I prefer to put all customizations out of the software package somewhere else. Would it be in Microservices or built as part of the ESB. I want to have the freedom to have the business logic as platform independent as possible. By moving the custom business logic out in webservices implemented by Microservices or part of the ESB I accomplish that. There are political aspects to this issue too? First the COTS vendor wants to have all the business logic customization in its application for the following reasons:

  1. The vendor wants to increase the $$$ from the custom development services they will provide.
  2. The vendor can enrich its application offerings and business logic by taking this customized business logic and generalizing it in future releasee.
  3. The more customizations and business logic embedded in the vendor logic the harder for the organization to switch to another competitor as they will the cost of customizations from scratch would add up.

The delivery department would prefer not to take ownership of new software components, especially if the organization does not have many software developers and depends on consulting companies.

My argument is that, all software be it ERP system like Dynamics AX or Time and Attendance systems is generic and the vendor offer it to your organization and your competitors. What differentiates your organization from your competitors is the custom process and business logic your organization uses. If you let the vendor build these customizations in their software then you end up subsidizing your competitor upgrade, and maybe giving them your edge. That is why I tend to recommend extracting any custom business logic new or modified and building it outside the COTS. Sometimes this is not possible due to the CTOS platform limitations or due to organizational standards. But whenever is possible extract any custom business logic outside of the COTS

Let me know your thoughts on that.

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