In this blog post, I discuss an app modernization approach that we call “modernize-by-shifting.” In essence, we take an existing application and move it to “managed” container hosting environments like Azure Kubernetes Service or Azure Service Fabric Mesh. The primary goal of this app modernization strategy is to undertake minimal possible change to the existing application codebase. This approach to modernization is markedly different from a “lift-and-shift” approach where workloads are migrated to the cloud IaaS unchanged with little to no use of cloud native capabilities.

Step One of App Modernization by Shifting

As the first step of this approach, an existing application is broken into a set of container images that include everything needed to run a portion of the application: code, runtime, system tools, system libraries, and settings. Approaches to breaking up the application in smaller parts can vary based on original architecture. For example, if we begin with multi-tier application, each tier (e.g. presentation, application, business, data access) could map to a container image. While this approach will admittedly lead to coarser-grained images, compared to a puritanical microservices-based approach of light-weight images, it should be seen as the first step in modernizing the application.

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