Cloud Migration Strategy: Monolith to Microservices

If your application is “cloud-ready”, then cloud migration can be quite painless. However, this is not the case for migrating most legacy monolithic applications to the cloud. Several cloud migration strategies have emerged to handle each type of scenario, with best practices evolving every day. Each Cloud Migration Strategy reviewed may not work for all Monolithic Applications, and cloud migration consulting may be needed to ensure proper planning. The benefits of cloud migration are profound, but the costs can be high. For some, the cost of not migrating to the cloud will prove to be even higher.

The term “Legacy Application” conjures up visions of COBOL, C, or some other arcane programming language. Ironically, these legacy systems are often a business’s mission-critical apps and can be difficult to replace. For these companies, a cloud-native rewrite of their application is either too risky or impossible, however, several app modernization strategies can partially leverage the advantages of microservices and enable the integration of new technologies.

Cloud Migration Strategy — Cloud Migration Strategies

Cloud Migration Strategies

Lift & Shift: Also known as “Rehosting”, this can be a good option for migrating applications that are cloud-ready to some degree.
Lift, Tinker & Shift: Making a few technology stack upgrades before migrating to the cloud (without changing the application’s core architecture) is also known as “replatforming”. This can provide accelerated cloud migration and tangible cost savings.
Partial Refactoring: Partial refactoring is when specific portions of an application are modified to take advantage of the cloud platform. This enables some of the new functionality of microservices without the cost & complexity of a complete refactor or rewrite.
Complete Refactoring: Short of a complete rebuild of your application in cloud-native formats, “refactoring” can be a viable option for moving significant functionality to the cloud. A gradual approach is possible (and advised), as new microservices can be quickly tested without impacting the reliability of the existing monolithic application. You can use microservices to create new features through the legacy API as you refactor the legacy platform one piece at a time. The least measured approach of these strategies, but still far less effort than a complete rewrite.

Application Migration to Cloud: There is No Need to Hurry

Regardless of which application modernization technique you use, retiring parts of your legacy monolithic application can be done thoughtfully over time, making it easier to implement within your organization. You can determine which parts of your application are easiest to refactor, and execute a little bit at a time. Also, the critical parts of your application not suitable for the cloud can be left on-premise and accessed through well-defined APIs. Finally, you may decide to “retire” rarely used functionality to lower your total cost of ownership (TCO).

The right approach for you will likely depend on several factors, including:

Cost & time constraints
How well-suited your application is to cloud migration (when not to modernize below)
Scalability requirements
Strong business need for adding functionality not possible with the existing application.
Agility requirements

Application Modernization: When Not To Do It

Not all applications are right for the cloud. This is especially true when you consider containerizing and service-enabling the applications. Below are a few guidelines:

The more technical debt you have, the harder it will be to get your application “cloud-ready”. Containers and services leverage a specific set of microservices patterns, and it may be easier and cheaper to start anew if your application does not incorporate these patterns. This is often the case with companies who have grown by acquisition, having stitched multiple platforms together with countless patches and complex APIs.
Tightly coupled monolithic applications are typically a poor choice for cloud migration. Decoupling the data from the application layer is required to benefit from Microservices and this often requires a rewrite of most of the application.
Modernizing outdated applications using old languages and databases may also be more trouble than they’re worth. It may be cheaper and less risky to do a cloud-native rewrite in these instances. Although new tools are being developed to “easily modernize” these types of applications, proceed with caution as they have significant limitations you should consider.

Cloud Migration for monolithic applications can be daunting, but with the right strategy and thoughtful planning you can mitigate risks, make incremental improvements, and get upper-management support throughout the cloud migration journey. Rehosting, Replatforming and Refactoring are each viable options, depending on your situation.