Deep customization of multi-tenant SaaS using intrusive microservices

Enterprise software needs to be customizable, and the customization needs from a customer are often beyond what the software vendor can predict in advance. In the on-premises era, customers do deep customizations beyond vendor's prediction by directly modifying the vendor's source code and then build and operate it on their own premises. When enterprise software is moving to cloud-based multi-tenant SaaS (Software as a Service), it is no longer possible for customers to directly modify the vendor's source code, because the same instance of code is shared by multiple customers at runtime. Therefore, the question is whether it is still possible to do deep customization on multi-tenant SaaS. In this paper, we give an answer to this question with a novel architecture style to realize deep customization of SaaS using intrusive microservices. We evaluate the approach on an open source online commercial system, and discuss the further research questions to make deep customization applicable in practice