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Code Legacy: Maintain, Modernize and Optimize
Many companies still rely on software developed years or even decades ago. These applications, often critical to day-to-day operations (customer management, invoicing, logistics, production...), are gradually becoming a hindrance: obsolete technologies, maintenance difficulties, lack of available skills and security vulnerabilities.
At IT Systèmes, we help organizations modernize their legacy code. We start from business usage to define the most appropriate trajectory: refactoring, encapsulation via API, containerization or migration to modern environments. All our developments follow SOLID principles, guaranteeing scalable, maintainable and secure software, in line with your strategic objectives.
What is legacy code?
Legacy code refers to software that is still in use but is based on outdated technologies—such as programming languages, frameworks, or databases—that are no longer actively maintained. A system is considered legacy when an entire component of the information system (IS) is built on these aging foundations.
It’s not a matter of age, but of risk. Legacy code is often critical to business operations—billing, customer management, production—but gradually becomes difficult to update: missing documentation, scarce expertise in the original technology, unpatched security vulnerabilities, and rising maintenance costs. The real danger isn’t that the application is old; it’s that it becomes a bottleneck that no one knows how to update safely anymore.
Modernizing legacy code does not mean rewriting everything from scratch. Depending on the business value and technical condition of each application, several approaches are possible: refactoring, encapsulation via APIs, containerization, or migration to current technologies. This is precisely the approach that IT Systèmes is implementing below.
Our expertise in Code Legacy
Audit and diagnosis of application assets
Refactoring and progressive optimization
Encapsulation and exposure via APIs
Migration to current technologies
Containerization and cloud readiness
Legacy application security and compliance
Why work with IT Systèmes?
- Reduce technical debt and maintenance costs.
- Modernize your software without interrupting production.
- Reinforce the security and compliance of your applications.
- Facilitate integration with your modern tools via APIs.
- Prepare your systems for the future with cloud-ready architectures.
Learn more:
→ Rebuild rather than maintain: our custom business software development.
→ Migrating applications to modern environments.
→ Keeping your applications up to date over the long term: third-party application maintenance (TMA).
Business analysis and application mapping
In-depth technical diagnosis
Definition of a progressive modernization plan
Refactoring, migration and security
Integration and continuous testing
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FAQ Code Legacy
Why modernize legacy software instead of replacing it entirely?
Complete replacement is risky and costly: it often involves total rewriting, service interruptions and loss of functionality for users. Progressive modernization enables you to retain critical functionality, ensure business continuity and reduce risks, while gradually migrating to modern technologies.
What are the possible approaches to modernizing a legacy application?
We combine several methods depending on the context: refactoring of existing code, encapsulation via APIs to make it interoperable, gradual migration to current frameworks and containerization to prepare for cloud operation. This tailor-made approach enables us to move forward step by step, without any break.
How long does a legacy code modernization project take?
How long this takes depends on the size and complexity of the application. A simple module can be modernized in a matter of weeks, while a complete system can take several months. Thanks to our progressive approach, we deliver tangible results quickly, reducing the tunnel effect and securing the overall trajectory.
How do you guarantee continuity of service during the modernization?
We implement transition strategies such as double-run, where the old and new systems temporarily coexist. Each modernized module is tested under real-life conditions before the switchover. This method avoids interruptions and guarantees gradual adoption by users.
What types of technology are you modernizing?
We work with a wide range of legacy languages and frameworks, such as Cobol, VB6, Delphi, older PHP frameworks, .NET Framework or legacy Java. We then migrate to modern environments such as .NET Core, Java Spring Boot, Python, Node.js, Angular or React, depending on your needs.
How do you ensure the security of older, often vulnerable applications?
Nous renforçons la sécurité en ajoutant du chiffrement, en modernisant l’authentification (MFA, SSO), en mettant en place de la supervision continue et en corrigeant les failles critiques. Nous renforçons également votre conformité réglementaire, notamment au RGPD, afin de sécuriser vos données et vos processus.
What's the impact on my internal teams?
We involve your teams throughout the project with workshops, user testing and training. A skills transfer is planned to enable them to take control of the new, modernized applications. This encourages adoption and reduces dependence on an external service provider.
What concrete benefits can my company expect from legacy code modernization?
You get applications that perform better, are more secure and interoperable with your modern systems. You reduce your maintenance costs, improve team productivity and prepare your IS for future developments such as the cloud or the integration of AI and data solutions.