The cloud is rapidly changing the way in which applications are designed and architected. We are shifting from monolithic applications to applications that are designed as loosely coupled services that can either communicate through APIs or are using asynchronous messaging and eventing. These applications need to be designed to easily scale horizontally, and new instances should be added or removed rapidly, and mostly automatically. 

This brings big challenges to the underlying architecture of your applications. Operations should be able to be processed in parallel and deployments must be fully automated. The system as a whole, with all the different services included, should be resilient when failures occur.

Monitoring and telemetry must be embedded for the system as a whole as well, to gain insights into the health and performance...

For an application to eventually become fully cloud-native, it should follow an iterative process called the cloud maturity model. The first two steps will either require minimal code or simply the configuration changes necessary to connect to Azure PaaS services or to optimize the application for cloud scale. Applications are moved to the cloud, but are mostly using the same code base as they were using when they were deployed on the on-premises systems. The last step, that is, the step to rebuild the application, will require a complete redesign and refactoring of the application. This step will be the most difficult and most intensive part of the application migration process.

The order of this process can be completely random. Organizations can decide to rebuild their applications from scratch to fully modernized applications immediately...

There are four migration strategies that are defined in the cloud maturity model: rehost, refactor, rearchitect, and rebuild. In the upcoming sections, these migration strategies will be explained in more detail.

Rehost is often referred to as lift-and-shift migration. When you rehost your applications to the cloud, each application is migrated as-is to the cloud. This technically means that you move the VMs or on-premises servers and put them into the cloud infrastructure. The applications that are installed on the on-premises VMs and servers are then moved in their original state, without any code changes or refactoring of the application.

You can use some of the managed...

In this chapter, we covered the value that application migration can bring to organizations. We introduced the different migration strategies that are available for migrating your applications to Azure, from a simple lift and shift to a complete rebuild of your application.

In the upcoming chapter, we are going to create a roadmap for application migration to Azure and discuss the different migration strategies.

Answer the following questions to test your knowledge of the information found in this chapter. You can find the answers in the Assessments section at the end of this book.

1. What values can migrating applications to Microsoft Azure bring to your organization?
   1. Reducing costs
   2. No investments in developing the skills of your developers
   3. Faster time to market
   4. IT simplification

2. What are the biggest pros of using the rehost migration strategy for your applications?
   1. No code changes
   2. Migrate quickly to Azure
   3. No infrastructure to manage
   4. Maximum cost reduction
3. Which migration strategy do you need to choose to start making use of the DevOps practices in Azure?
   1. Rehost
   2. Refactor
   3. Rearchitect
   4. Rebuild

You can refer to the following links for more information about the topics covered in this chapter:

• Azure Application Architecture Guide: https://docs.microsoft.com/en-us/azure/architecture/guide/
• Application Modernization with Microsoft Azure: Build 2018: https://www.youtube.com/watch?v=kcHhMjymt_0
• Migrate to the cloud: https://www.microsoft.com/net/learn/architecture/migrate-to-the-cloud
• Azure Migration Center: https://azure.microsoft.com/en-us/migration/
• Cloud Migration Essentials: A guide to migrating servers and virtual machines: https://azure.microsoft.com/en-us/resources/cloud-migration-essentials-e-book/