The Hidden Pitfalls of Rehosting: Painting Yourself into a Corner

author Adam Hamšík
CEO & Co-Founder

While lift & shift offers speed and minimal disruption, it can lead to significant challenges down the line. Here’s why.

Rehosting, commonly known as the “lift and shift” approach, is often the quickest route to cloud migration. It involves directly moving applications from an on-premises environment to the cloud without any modifications. While this strategy offers speed and minimal disruption, it can lead to significant challenges down the line.

The Double-Edged Sword of Pay-as-You-Go

The cloud’s pay-as-you-go model is attractive because it promises cost savings based on actual usage. However, this model works both ways:

  1. Minimal Usage, Minimal Costs: If your cloud usage is low, you’ll enjoy reduced costs.
  2. High Usage, High Costs: Conversely, if your application, especially a non-optimized one, starts consuming more cloud resources, the costs can skyrocket. And if your application isn’t architected for the cloud, optimizing these costs post-migration can be challenging and time-consuming.

Optimal Costs and Good Architecture

In the cloud, the adage “optimal costs are a transitive property of good architecture” rings true. Simply put, to achieve cost efficiency in the cloud, you need a well-architected application tailored for the cloud environment. Look for cloud best practices like the excellent AWS Well Architected framework for help with architecture decisions.  Rehosting, by its very nature, bypasses this architectural optimization, leading to:

  1. Suboptimal Resource Utilization: While cloud platforms offer scalability and the ability to shut down unused resources, these benefits can only be fully realized if the application is designed to leverage them. Traditional on-premises architectures often lack these properties, making them ill-suited to capitalize on the cloud’s dynamic resource management capabilities.
  2. Hidden Technical Debt: Moving an application to the cloud without modifications means transporting all its existing issues, bugs, and technical debt. Over time, this debt can accumulate, leading to performance issues, security vulnerabilities, and increased maintenance costs.

For anyone looking to migrate their workload to cloud we have gathered the following hints:

  1. Strategic Changes with Profound Impact: Look for Specific, strategic changes, that can lead to significant benefits. E.g we saw almost 80% reduction in required compute resources after migration from php-fpm to openswoole php engine. Such targeted modifications can drastically improve application efficiency and lead to enhanced user experiences and substantial cost savings.
  2. The Challenge of a Complete Rewrite: Undertaking a full application rewrite is akin to reconstructing a building from its foundation. Teams face the daunting task of maintaining the existing application while simultaneously developing the new, refactored version. This dual responsibility can stretch resources and introduce challenges, especially when there are demands for new features or changes in the existing application during the refactoring process.
  3. Post-Migration Refactoring: Be aware of migrate first and refactor later approach. It’s not uncommon for refactoring to be a post-migration consideration. Organizations might initially opt for a simpler migration strategy to quickly move to the cloud. However, once in the cloud environment, the potential inefficiencies and the allure of cloud-native features often make a compelling case for refactoring.
  4. Pick a good vendor: AWS has a largest number of available cloud services and with largest market penetration. This makes it a reliable partner for which customers can find developers, devops engineers and cloud architects. 
  5. Cloud vendor migration support: Try to follow your vendors migration best practices like AWS Migration Acceleration program. This can help you with covering migration costs, development and event help to modernize your applications.
  6. Experience Matters: The replatforming journey can be complex, but having an experienced migration partner can make a world of difference. Engaging with a partner who has a track record of successful cloud migrations, and helped customers replatform their applications can provide valuable insights, best practices, and accelerate the whole process.

Security and Financial Implications

Rehosting can inadvertently expose organizations to heightened risks:

  1. Old Bugs and Security Issues: Moving applications with existing vulnerabilities to the cloud can amplify the risks. In the cloud, a security breach can have far-reaching consequences, both in terms of data integrity and financial implications.
  2. Unlimited Spending: In on-premises setups, resource constraints naturally limit the fallout from bugs or issues. In the cloud, a runaway process or a misconfigured resource can lead to unlimited consumption, resulting in unexpected and substantial bills.

Final Words

Rehosting, while offering a quick path to cloud migration, can lead organizations into a corner, riddled with escalating costs, technical challenges, and heightened risks. It’s crucial for organizations to understand the long-term implications of their migration strategy. The allure of quick migration should be weighed against the potential challenges and costs that might arise in the future.


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