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Legacy Application Migration: Six-Step Guide

Often, business owners decide to continue maintaining outdated software systems because they think legacy system migration, part of application modernization services, would cost much more. Although this tactic may be viable short-term, using legacy systems can cause a lot of problems in the long run.


Clinging to legacy applications requires regular spending on maintenance, training specialized personnel, resolving compatibility issues, and making frequent patches to repair failed components. Read on and find out how to avoid these issues with legacy to cloud migration.

What is legacy migration?

Legacy systems are software applications that have become outdated or obsolete but are still in use by a business to support some critical processes. Oftentimes, companies rely on these applications for years before discarding them. For example, it can be legacy CRM software, ERP systems, accounting solutions, and other applications.

In most cases, legacy software acts as a handicap to business evolution, threatening productivity, flexibility, and security. Legacy application migration is the answer to revitalizing your system and involves the adoption of modern technologies.

The legacy systems migration process is unique for every instance but should never interrupt existing business processes. When talking about legacy application modernization, the two possible options are lift-and-shift and refactoring. To avoid too many interruptions, application refactoring can be done in iterations after moving to the cloud with lift-and-shift.

Why should businesses migrate?

Migrating legacy software allows companies to keep up with modern tech trends, to approach industry challenges more effectively, and provide a much better user experience to their clients. Here are some more reasons businesses should choose to upgrade their applications:

  • Legacy apps aren't easily scaled to support greater functionality.
  • Legacy apps are not compatible with modern tools and apps.
  • Legacy apps often lack alternative versions to support mobile devices.
  • Legacy apps run under old design patterns offering low performance.
  • Legacy apps are a growing security threat because of outdated design loopholes.

These factors cripple your business’ productivity, create redundant expenses, and make you lose to your immediate competition. That’s why legacy migration is what every company should consider.

Why migrate to the cloud?

One of the most efficient ways of migrating legacy applications is moving them to the cloud. Let's look at the advantages of cloud adoption over maintaining legacy applications.

Lower expenses. By using cloud services, businesses only pay for what they actually use and can easily upscale or downscale their resources. At the same time, cloud providers take care of maintenance and software updates, and provide a variety of services that do not come with any additional costs.

Easier access and mobility. Cloud-based applications offer high availability and provide support for modern user devices. This means your systems can be accessed 24/7 from anywhere and even allow multiple users to work with data at the same time.

Increased scalability. Not only can companies upscale and downscale their apps to increase storage capacity, but they can also add cloud services to enable new features or enhance application performance monitoring. Applications can also be integrated with other SaaS apps running in the cloud.

Improved data security. Cloud systems are regularly updated to comply with security standards and offer built-in security mechanisms such as permission-based rules, policies, security analytics, and enterprise visibility tools.

Why don’t more companies migrate legacy applications?

The reason many companies still hold on to their legacy applications, reluctant to migrate, is that migration is generally an intensive process that involves a lot of stress for both the business owners and the business itself. The challenge is to transition smoothly enough, wit no critical disruptions that may lead to losing revenue or disappointing users with a poor experience.

The main reasons more companies don't migrate their legacy apps are:

  • The application still serves its purpose, so there's no pressing need to replace it.
  • The company does not want to cause any interruption to business processes.
  • The company is afraid of the costs of developing and replacing the application.

It's always good to remember that risks come with any step in business evolution and they can be anticipated and mitigated. The rewards you gain after a transition often outweigh the risks and making this step first among others puts you ahead of the competition.

Why do some legacy migrations fail?

Migrating legacy applications is not a straightforward process and it may go astray without proper preparation and implementation. A good outcome comes when business minds meet with experienced technology experts to come up with a migration strategy and then follow best practices to execute it.

However, sometimes projects fail, and here are the most common reasons:

  • Poorly designed, developed, or documented legacy systems can lead to serious complications during redesign and transition.
  • Lack of a proper strategy and execution plan can lead to multiple setbacks and unpredictable situations during migration.
  • Ignoring the user experience and only focusing on the platform transition can make migration efforts futile.
  • Migrating Legacy apps and their dependencies can cause system breakdowns when they are poorly evaluated.
  • Productivity issues, such as network downtime and data access problems during migration, can cause significant business disruption.
  • Legacy system upgrades can be time-consuming, potentially leading to budget overruns and causing companies to maintain their existing systems.

If you are having these issues, a good idea is to partner with the software development and cloud migration team. Technology experts can offer their in-depth knowledge, broad expertise, and strategic thinking to assist you in legacy application migration.

What are legacy migration options?

You can take several paths on your way to legacy migration. The options include rehosting, re-platforming, and refactoring your applications. Let's take a closer look.

Application rehosting

Rehosting is the easiest way to cloud adoption. Using this method, applications are moved from the on-premise to the cloud environment without any changes to the codebase. You are simply lifting and shifting to the cloud. This way the app can not access advanced cloud capabilities like autoscaling, but it still acquires general cloud hosting advantages like 99.999% reliability and global access.

Businesses often use rehosting as the first step in their migration process. Once they've completed the move to the cloud, it's much easier to modernize their legacy software.

Application re-platforming

During re-platforming applications are optimized for cloud compatibility and better performance. Slight changes are made to the software architecture to enable using cloud-based services like containers, DevOps automation, and modern database management. Businesses can also enable autoscaling to efficiently manage cloud resources.

This option works great when an application is hardwired to a certain workload and the business urgently needs improving scalability and performance. It's also the top choice when you'd like to take advantage of cloud capabilities but don't want to completely redesign the app's architecture.

Application refactoring

Refactoring is the complete remodeling of the application architecture and business logic in order to refine its design model, database utilization, and coding techniques. At the same time, the app's functionality and user experience remain intact. It also involves complete optimization for the cloud to fully take advantage of its capabilities.

Refactoring should be chosen when the business is ready to completely transition to a cloud-native architecture. Reworking the codebase will make it cleaner, easier to update, and better performing.

Full Stack Modernization

Legacy applications sometimes require a thorough revamp of both front-end and back-end technologies. This is especially common in enterprise applications built with older software frameworks. This often involves transitioning from .NET Framework to .NET Core for back-end operations and from AngularJS to Angular for front-end development.

Transitioning from .NET Framework to .NET Core

Microsoft's modern, open-source, cross-platform framework .NET Core, enhances your application's performance, flexibility, and efficiency. If you built your legacy application with the .NET Framework, transitioning to .NET Core can substantially improve performance, ensure cross-platform compatibility, and align your work with modern development practices.

Transitioning from AngularJS to Angular

AngularJS, once the favored choice for front-end development in many enterprise applications, has been outpaced by the evolution of technology. The newer versions of Angular have since taken its place.

Transitioning from AngularJS to Angular introduces a range of benefits to your application. Angular, a modern and feature-rich framework, ensures better performance, scalability, and enhanced tooling. It evolves with your application's expanding needs, maintaining efficiency and responsiveness throughout.

Learn more about what Angular can do for your application in our comprehensive Angular Migration Guide.

How to Successfully Migrate Your Legacy Application

Every legacy application is unique from a technical standpoint. That's why it's vital to analyze the system's infrastructure needs, dependencies, integrations, data requirements, security and compliance policies. We recommend taking the following steps for legacy migration to the cloud:

1. Carry out a SWOT analysis

Documenting the migration project's strengths, weaknesses, opportunities, and threats will allow you to create a bird’s-eye view over everything: from operational to business and technical aspects. It's a vital part of creating a sound strategy for moving to the cloud.

Strengths make the migration so rewarding, like the scalable storage, improved disaster recovery, and SaaS model business advantages.

Weaknesses are the possible obstacles posed by cloud adoption like the downtimes during migration, running over budget, or the lock-in to a single cloud service provider.

Opportunities are what your business gains after legacy migration, like the opportunity to tap into disruptive technology such as machine learning and data science.

Threats are the dangers of compromising your business and its reputation and include putting your data into public servers.

2. Evaluate your environment

One of the key steps is analyzing your existing workloads and pinpointing key infrastructure, such as network, storage, and computing resources. You will also need to define critical performance and availability requirements. After that, you can use automated tools like Azure Migrate or AWS Server Migration Service to map your existing system to the cloud and configure maintenance settings.

3. Set up your migration strategy

This step involves choosing one of the legacy migration options described earlier and preparing comprehensive documentation detailing every aspect of its implementation. It is highly advisable to create a backlog and assign issues to your technical team to track their performance. We also recommend appointing a project manager that will help communicate the details of migration between stakeholders.

4. Carry out a pilot migration

A pilot migration is a good way to test out your strategy and see whether your users are satisfied with the new experience. Run your pilot migration through testing and quality assurance to make sure you avoid any disturbance during the actual migration.

5. Migrate your legacy applications to the cloud

Don't rush by discontinuing your legacy system right away. You can make the transition gradually and at the same time prepare your users. The old software could be kept running in parallel and used as a backup system until you are fully sure of a successfully completed migration.

6. Cloud maintenance and optimization

With the power of the cloud comes great responsibility. Now that you've migrated, you need to monitor, optimize, and manage your performance in the cloud. Keep track of your usage reports and configure autoscale to provide better cost management.

Support your legacy application migration

Legacy applications drags you down while competitors keep climbing higher and embracing modern technologies. The cloud helps companies transition to an on-demand, software-as-a-service model that reinforces their business evolution.

Decomposing legacy systems which often have no documentation and creating a strategic plan for migration requires high technical expertise and deep knowledge of software infrastructure. Preventing system downtime and business disruption during migration is another issue.

Seeking assistance from an experienced cloud migration partner can save you a lot of stress before, during, and after your legacy application migration.

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CTO / Department Head / Partner
I've been leading a department specializing in custom eLearning software development and Business Intelligence software development for 17 years.
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