AIMultiple ResearchAIMultiple Research

The Complete Guide to Legacy App Modernization in 2024

As a result of the increasing competition among businesses and external factors such as the pandemic, companies have considerably accelerated their digital projects. However, existing legacy apps can be a roadblock in the path to digital transformation. For example, nearly a third of organizations believe that the inability to integrate modern and legacy applications and inoperability between multiple systems will limit their organization’s capabilities. 

Thus, improving legacy systems and applications is one of the core elements in modern businesses’ digital transformation journey.

What is legacy application modernization?

Legacy app modernization is the practice of updating, upgrading, or improving existing legacy apps that have become obsolete such that they no longer function properly and fail to meet business needs. App modernization is a common component of a business’ overall digital transformation strategy.

Why modernize legacy apps?

The pace of change in the IT landscape is fast as every new year brings new technologies and new versions of older apps. Inevitably, existing applications of a business get outdated and cause business problems. Some common challenges that face legacy apps today include:

  • They no longer receive support and maintenance from their developers
  • They are incompatible with modern solutions
  • They are monolithic (e.g. built as a single and indivisible unit) so it’s challenging to update and scale them
  • It gets harder to find specialists to work with legacy systems
  • They incur high maintenance costs
  • They may contain known or unknown security vulnerabilities

As a result, legacy apps become an obstacle to business activities and require enterprises to update, rebuilt, or replace them.

What are different approaches to app modernization?

Common approaches to app modernization include:

  • Rehosting, also called replatforming or “lift and shift”, involves moving components of an application to modern hardware or cloud. Rehosting may or may not require substantial code changes according to the compatibility between the app and the host platform. 
  • Rearchitecting involves altering and optimizing the existing code to improve the performance of a legacy system and to enable new capabilities. Rearchitecting is meant to upgrade the current application rather than building a new one.
  • Rebuilding involves rewriting the app components’ code from scratch while preserving its scope. To rebuild an application, companies can identify the components to modernize and rewrite them in turn. This can be a better option than writing an entire application from scratch.
  • Replacing is abandoning the existing application and rewriting or replacing it with an off-the-shelf solution. Replacing is an extreme approach and can be costly. However, if the other three approaches are not sufficient to modernize an app to meet business needs, replacing can be the best option.

What are the benefits of legacy app modernization?

Reduced costs

Modernizing outdated apps can save businesses from costs associated with them. For example:

  • Legacy apps are costly to maintain as they operate on outdated technologies. For instance, according to the U.S. Government Accountability Office’s report, the federal government’s legacy systems, such as those running on the outdated programming language COBOL, cost about $337 million per year to operate and maintain.
  • Legacy apps are hosted on-premises data centers which are costly to maintain. Leveraging cloud services can enable businesses to cut total costs up to 50%.
  • Hiring skilled personnel for legacy systems is also costly since new developers don’t learn outdated technologies and older specialists become rare.

Increased productivity

Legacy apps were not designed to work with modern systems and hardware. Compatibility issues are common with legacy apps which can hinder productivity. Employees may struggle with lags, bugs, and other errors without reliable support from the developer of the app.

Furthermore, modernizing old systems can enable businesses to create a smoother working environment between teams as different modern software applications can facilitate communication more efficiently. 

Improved security

As mentioned above, legacy systems may contain known or unknown security issues since they weren’t developed using modern information security practices. Attackers can exploit these issues to gain access to an organization’s network.

Modern apps receive constant security upgrades and bug fixes against new types of threats. Using supported technology is one of the most important steps for businesses to ensure data security.

Cloud migration

Cloud migration is one of the most common practices in modernization processes. Public, private, or hybrid cloud services enable businesses to scale their apps easily and at a lower cost than on-premise infrastructures.


Modern businesses often rely on different environments to run apps such as on-premise platforms and cloud infrastructures. Containerization enables businesses to run apps consistently and efficiently across different systems and platforms.


Microservices, also called microservice architecture, is an application architectural style consisting of a loosely coupled collection of services rather than a monolithic structure. Microservice structure enables businesses to deploy different components of an application independent of each other. This means they are easier to maintain, upgrade, and scale than a monolithic application.

For more on different digital transformation strategies, check our article on digital transformation frameworks.

If you still have questions about legacy application modernization, we would like to answer them:

Find the Right Vendors
Access Cem's 2 decades of B2B tech experience as a tech consultant, enterprise leader, startup entrepreneur & industry analyst. Leverage insights informing top Fortune 500 every month.
Cem Dilmegani
Principal Analyst
Follow on

Cem Dilmegani
Principal Analyst

Cem has been the principal analyst at AIMultiple since 2017. AIMultiple informs hundreds of thousands of businesses (as per similarWeb) including 60% of Fortune 500 every month.

Cem's work has been cited by leading global publications including Business Insider, Forbes, Washington Post, global firms like Deloitte, HPE, NGOs like World Economic Forum and supranational organizations like European Commission. You can see more reputable companies and media that referenced AIMultiple.

Throughout his career, Cem served as a tech consultant, tech buyer and tech entrepreneur. He advised businesses on their enterprise software, automation, cloud, AI / ML and other technology related decisions at McKinsey & Company and Altman Solon for more than a decade. He also published a McKinsey report on digitalization.

He led technology strategy and procurement of a telco while reporting to the CEO. He has also led commercial growth of deep tech company Hypatos that reached a 7 digit annual recurring revenue and a 9 digit valuation from 0 within 2 years. Cem's work in Hypatos was covered by leading technology publications like TechCrunch and Business Insider.

Cem regularly speaks at international technology conferences. He graduated from Bogazici University as a computer engineer and holds an MBA from Columbia Business School.

To stay up-to-date on B2B tech & accelerate your enterprise:

Follow on

Next to Read


Your email address will not be published. All fields are required.