What is a Legacy System in Software Development? [Definition]

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What is a Legacy System?

A legacy system refers to an outdated computer system, software application, or technology infrastructure that is still in use. These systems rely on an obsolete programming language, technology or hardware component.

The term “legacy” itself doesn’t imply outdated but rather signifies that the system has a history and heritage. A legacy system exhibits several key characteristics that distinguish it from its modern counterparts.

Let’s check out the main characteristics.

A Legacy system relies on outdated programming languages or hardware, resulting in performance limitations and challenges in finding skilled maintenance personnel.
When technology evolves, vendors often stop supporting older systems, leaving limited resources for troubleshooting and problem resolution.
A Legacy system requires specialized expertise, leading to increasing maintenance costs and budget constraints.
These systems lack flexibility and can’t easily adapt to changing business requirements, potentially impeding growth and innovation.
Due to infrequent updates, a legacy system is more vulnerable to security breaches, risking unauthorized access to sensitive data.

In deciding whether an organization should retain, upgrade, or replace a legacy system, understanding what it is and what its characteristics are is crucial.

What are Legacy Applications?

In software, legacy applications are those programs or applications that have been running for years, or even decades. These so-called legacy applications are characterized by their outdated technology, codebase or status of having been left off the shelf.

These applications have thus become known as legacy applications for their long-term use and the difficulty in upgrading to new technological standards. Their characteristics often include reliance on outdated programming languages, compatibility issues with contemporary systems, and a lack of support or updates from their creators.

Why Do Organizations Still Use Legacy Systems?

Here are the reasons why organizations still use legacy systems.

Historical Investment: Organizations have made substantial financial investments in developing or customizing legacy systems, making replacement costly.
Data Retention: Legacy systems house critical historical data essential for business operations, compliance, or analysis, making data migration complex.
Business Continuity: Legacy systems are deeply integrated into workflows, and transitioning can pose significant risks to business continuity.
Regulatory Compliance: Strict industry regulations may necessitate the use of legacy systems, with replacement involving lengthy certification processes.
Lack of Expertise: A lack of skill in legacy systems can also hamper migration to new technologies.
Risk Aversion: There are risks stemming from perception, such as the fear of loss of data, downtime in system functions or operational disturbances. These indirectly facilitate the retention of legacy systems.

5 Common Challenges Faced with Legacy Systems

Here are the common challenges faced with legacy systems.

Lacks Compatibility with Modern Systems
Legacy software may struggle to integrate or interact with modern software, hardware, or external systems, leading to compatibility problems that hinder seamless operations.
Prone to Security Vulnerabilities and Risks
At the same time, these legacy systems are no longer being patched or updated, which exposes them to the threat of cyberattack, posing a serious risk to sensitive information and operations.
Difficult in Achieving Scalability
Another issue is that legacy systems prove unreasonably inflexible and unable to scale to support growth or meet the evolving demands of the business, making it difficult for a company to grow or transform.
Challenging in Ongoing Maintenance and Support
With so many legacy systems, finding skilled professionals to maintain and repair them is in itself challenging, let alone when these know-how techniques become a thing of the past.
Incurs High Operational Costs and Expenses
Legacy systems can be costly to maintain, with expenses related to hardware upkeep, software licenses, and specialized support contributing to a significant financial burden.

Updating and Transitioning Legacy Systems

Updating legacy systems is essential for organizations aiming to modernize their technology and remain competitive. This process involves several key steps:

Comprehensive Evaluation: Begin with a comprehensive evaluation of the existing legacy software and define software modernization goals.
Modernization Strategies: Organizations can choose from various legacy system modernization strategies based on their specific needs.
Data Migration: Carrying out successful data migration from the old systems to new systems is a vital process. The collected data must be properly transmitted, and integration with the existing or replacement of other systems should keep right on working.
Testing and Quality Control: Stringent testing and quality controls are essential to ensure that all problems have been ironed out before the implementation of the newly revised or transitioning system. That is, functional testing, to measure performance and ensure security in a way that is compatible with the system’s objectives.
End-user Preparation: Preparing end-users for the updated or newer systems is crucial. Training programs should be in place to ensure that employees can effectively utilize the new technology.
Post-transitional Support: Finally, post-transitional support and further monitoring are highly desirable to improve system performance and overcome any problems that may arise.
Documentation: Keeping good, clear documentation as the process proceeds from beginning to end is important for future reference and troubleshooting.

When planning modernization strategies, businesses like yours tend to choose reputed vendors who provide reliable application modernization services to revamp your legacy apps. These services play an important role in ensuring a successful transition and maximizing all the benefits of updated systems.

Real-life Examples of Legacy Systems

Here are the top 3 examples of legacy systems.

IRS Individual Master File (IMF) System
The IRS IMF system is a legacy platform used by the U.S. Internal Revenue Service to maintain records of individual taxpayers and process their returns.
- First established in the 1960s, it holds all of an individual’s most important tax information.
- Despite its age, it remains a foundational system for tax collection in the United States.
- The challenges of migrating to a modern system while ensuring data accuracy have contributed to its continued use.
Sabre Reservation System
The Sabre reservation system, from the 1960s, is one of these legacy systems. It’s used by everyone to make airline or hotel reservations and bookings.
- This is one of the world’s earliest computerized reservation systems and provides the foundation for travel bookings.
- Sabre continues to handle an immense volume of transactions daily, despite newer competitors in the travel technology sector.
- Maintaining system reliability and data integrity is essential due to its critical role in the industry.
New York City Subway MetroCard System
One example is the New York City subway fare system, which introduced a card payment system for fare collection in the 90s but remains using this same legacy technology today.
- While the development of newer contactless payment methods has supplanted this, still millions of swiped MetroCards can be seen every day crossing the city’s subway stations.
- As part of the New York City transport network, it has been around for decades and demonstrates how some venerable technologies survive.
- How to balance a transition toward these more modern payment methods against legacy MetroCards poses the next logistical problem.

The three cases above clearly indicate that there are still many legacy systems out there, with different natures and purposes in every field of endeavour. For those who are curious as to how the modernization of legacy systems might proceed, you can check out our guide on application modernization. This will give you detailed knowledge about how to improve and upgrade legacy software applications.

In summary, legacy systems, with their historical significance and unique challenges, remain integral to many organizations. From handling tax files, and mail order travel to collection of subway fares–such systems are best described as the eternal stories of technology.

Of course, there are challenges with these legacy systems, including that they keep key operations running. With new technology coming along all the time, organizations need to decide how best to strike a balance between maintaining old systems and using modern approaches.