A legacy system refers to an outdated or obsolete software application, technology, or hardware that is still in use within an organization, often because it continues to fulfill essential business functions. Despite being outdated, legacy systems can be deeply integrated into an organization's operations, making them difficult and costly to replace. These systems may lack compatibility with modern technologies, suffer from performance issues, and pose security risks due to outdated software and hardware. However, the cost, complexity, and potential disruption of migrating to a new system often lead organizations to continue relying on legacy systems, even as they age.

Managing legacy systems presents significant challenges, including maintaining and supporting outdated technologies, integrating them with newer systems, and addressing the risks associated with their continued use. Organizations must weigh the risks and benefits of maintaining a legacy system against the potential advantages of modernization. In some cases, businesses choose to gradually phase out legacy systems, replacing them with more modern, scalable, and secure alternatives. However, in highly regulated industries or where critical operations depend on legacy technology, organizations may opt for a hybrid approach, maintaining the legacy system while integrating new technologies to extend its life and functionality.