What is the service model that poses the most challenges for migration due to increased levels of lock-in?

The service model that poses the most challenges for migration due to increased levels of lock-in is Software as a Service (SaaS). In the SaaS model, applications are hosted and managed by a third-party provider, and users access them over the internet. This setup often makes it difficult to migrate data and applications to another service provider or back on-premises due to proprietary formats, integration complexities, and the way data is structured and stored within the provider's ecosystem.

When organizations use SaaS applications, they typically become dependent on the vendor's infrastructure, APIs, and specific functionalities. If a company wishes to switch to another vendor or even bring the application in-house, it may face significant challenges due to the lack of control over the underlying infrastructure, data export limitations, and the potential need to reconfigure processes or retrain staff on new systems. Furthermore, customizations can further complicate migration efforts, as those custom features may not be replicable on another platform.

In contrast, Infrastructure as a Service (IaaS) and Platform as a Service (PaaS) models generally provide more flexibility, making it easier to migrate applications and data, as users maintain greater control over their environments. XaaS (Anything as a Service)