Brushing the Rust Off Your Software. The Importance of Legacy Migration

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The reasons a specific company keeps using legacy software may vary. Some don’t want to change anything if an app performs its business functions. The others are afraid of costs related to designing, testing, and deploying the new app. And there’s always somebody who just doesn’t want to change the habitual way of doing things. Add a minor change into traditional workflow, and everything will turn into chaos. That’s how they see it. However, the results of using a legacy system are always the same. For example, security issues, bad availability, poor compatibility, etc.

Fortunately, there’s a way out of this unpleasant situation. Even two ways, to be precise. You can either build a new system from scratch or take the best of the outdated application you work with and turn it into something useful. Today, we’ll consider how legacy system migration can breathe new life into the apps you use and into your company as a whole.

What’s a Legacy System and Why Migration is Important

First, it’s crucial to determine which application we can consider an example of legacy software. Today, development technologies evolve so fast, you can’t tell anymore whether your five-year-old CRM app is still competitive or not. The good news is , it’s not the age that turns a specific app into legacy software, it’s the tech used.

Therefore, if you adopted a brand new CRM application five years ago, it was designed and built properly, and you didn’t forget to pay due attention to the maintenance process, most probably it’s not legacy software and migration is not required. However, the tech stack that was used during the development phase plays a significant role. The reason is that one of the distinguishing features that every outdated system has is the inability to perform further development. For example, an outdated database management system can block your ability to integrate a new functional module into your system. Also, legacy systems are hard to support and maintain if you don’t perform the migration process timely. To see how such projects are done, you can check this case of re-designing a SaaS CRM, performed by our development team:

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Using legacy apps won’t necessarily ruin your business. Many companies can successfully run applications built with outdated technologies and don’t bother themselves with things like app migration. For example, the US banking system still largely relies on COBOL, a programming language that is over 60 years old. There are more advanced programming languages nowadays, and not so many people want to learn COBOL, so the overall number of specialists that the market has to offer shrinks every year. However, the overall system is so complicated that nobody dares to rebuild everything from scratch and perform the migration.

Read Also How Legacy Software Modernization Helps Replacing Hidden Costs With Obvious Benefits

Small companies, however, have more flexibility in terms of software migration. Therefore, if you think that the maintenance cost and time became unbearable, functionality left much to be desired, your clients’ data isn’t safe anymore, or you can’t comply with laws and regulations, maybe it’s time to think about modernizing your legacy software. Here, you have two major options. You can choose modernization, which implies upgrading the system, so it follows the current industry standards. As an alternative, you can prefer legacy system migration. Here, the applications that you use will be left behind, and you start using brand new software.

Two Ways to Perform Migration

There are two major approaches to legacy apps migration. One-shot migration is a more straightforward way of doing things. Here, you update the entire system in one go. In case of a large application, it’ll require thorough planning from a company providing software modernization services since the customer may incur losses in case of downtime. One-shot legacy system migration will better suit those companies that rely on a system that operates following a single standardized protocol and want to switch to its updated version quickly. Those who use a simple solution not integrated into an enterprise system can also choose one-shot migration.

The major advantage of this migration approach is that the overall process does not require much time. The switching between your legacy system and the new application occurs immediately, without causing delays in the company's work. Also, it’ll be easier to predict and fix the overall price of such an operation.

Read Also Antiquities That Harm. The Risks of Using Outdated Software

Another option is parallel-run migration. In this scenario, your application evolves gradually. Multiple tasks are performed simultaneously to ensure that features from the outdated app can be transferred to the new application, causing no issues. A middleware solution can regulate the load between the legacy system and the already implemented parts of a new application. Its usage is required until the new version of software is done and the migration process is considered successfully completed.

Parallel-run migration must be a preferable option for almost all applications. This approach guarantees that the development team won’t face any unpredictable problems since they can move one step at a time. Large legacy systems that cover the needs of all departments of your company and provide data exchange between them, so they can’t be modernized at once. Also, by performing the migration process gradually, you can test how end-users will react to new features and make adjustments if needed.

Steps For Successful Legacy System Migration

First, it’s important to assess the current state of software you use. Not all your applications require urgent migration. Scrupulous audit of your system will help to understand which parts of it can be considered legacy software, which of them will work just fine after a few adjustments, and, who knows, maybe there are no problems at all and you can use your software for another year or two with no issues.

If you decide that migration is the only way for you to stay afloat, the next step is the analysis of the infrastructure you have. It’ll help to understand how your legacy application functions, which will make, for example, migration to the cloud much easier. Most probably, there’s some useful documentation that can shed some light on how everything works, or at least how it reacts to specific inputs and what outputs it generates. Also, this process is necessary to understand the network and data architecture of a legacy app better.

As with any other complex task, legacy application migration requires a solid plan. There are different migration strategies that have different purposes and results. For example, lift and shift is a process where you take a system “as is” and migrate it to the cloud. Application evolution will cost you more and implies that you move the legacy system to the cloud piece by piece. Application re-architecting will change your legacy application beyond recognition. It’ll be rebuilt to introduce more agility and some feature enhancements after the migration process is complete.

After you backup everything to ensure there will be no problems with rolling back to the previous app version, you can re-engineer the legacy software. The migration process is not only about moving the application from decades old on-premise servers into the cloud to make it more accessible. Besides this, you must optimize the tech stack to help future generations of developers to maintain the system, integrate new functionality, and fix bugs. Detailed migration documentation will also help with these tasks, so it must not be underestimated.


Legacy system migration, despite the name, implies more than just moving an application from one place to another. The consequences of using outdated technologies and design patterns won’t go anywhere in this case. Without a deep understanding of architectural flaws and used tech stack, you risk spending time and money and, as a result, not receive all the advantages that a solid modernization strategy can give. Therefore, make sure you deal with the industry specialists if you decide to modernize your software.