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.

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Our expertise in Code Legacy

Audit and diagnosis of application assets

We take stock of your existing applications, analyzing code, dependencies, available documentation and associated databases. This audit highlights technical debt, security risks, maintenance costs and business priorities.

Refactoring and progressive optimization

Rather than rewriting everything, we prefer to modernize in stages. Refactoring involves improving code structure, eliminating technical debt and enhancing security, while retaining existing functionality. This approach extends software life and reduces costs.

Encapsulation and exposure via APIs

To make your legacy applications interoperable with your modern tools, we develop APIs around your existing modules. This enables you to connect your legacy software to your IS without immediately replacing it, and to move gradually towards a modern architecture.

Migration to current technologies

When legacy code can no longer be optimized, we gradually migrate to current technologies such as .NET Core, Java Spring Boot, Python or Node.js. We ensure compatibility with your cloud (Azure, AWS, GCP) or on-premise environments, while minimizing service interruptions.

Containerization and cloud readiness

We transform your monolithic applications into modern services using Docker and Kubernetes. This containerization facilitates deployment, improves scalability and prepares your software for operation in hybrid or multi-cloud environments.

Legacy application security and compliance

Legacy software often has critical vulnerabilities. We strengthen their security with encryption, modern access management, continuous monitoring and compliance with RGPD and ISO 27001 standards.

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.

A clear, rapid and personalized approach

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Business analysis and application mapping

Together with your teams, we identify critical applications, their role in your processes and business priorities, to define a realistic and secure modernization path.

In-depth technical diagnosis

We audit code, dependencies, databases and infrastructure to assess technical debt, risks and impacts on business continuity.

Definition of a progressive modernization plan

We establish an appropriate roadmap: refactoring of certain bricks, encapsulation via API, migration of modules, containerization. The aim is to avoid interruptions and deliver continuous value.

Refactoring, migration and security

We modernize legacy code according to defined priorities: quality improvement, migration to modern frameworks, integration of security by design. Each step is validated to guarantee business stability.

Integration and continuous testing

We test each evolution with real data sets, set up double-run phases (old and new systems in parallel) and validate application compatibility before going live.

Your IT experts

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Nadia

Accountant

Oxana

Marketing

Valentin

Computer engineer

Samuel

Project Manager

Laure

William

ModernWork technical manager

Peter

Project Manager

Arthur

Computer technician

Florent

General Manager - Partner

Anaïs

ADV

Johana

Computer technician

Emmanuel

Operations Manager

Matthias

Account manager

Thomas

Computer engineer

Adrien

Computer engineer

Amir

Developer

Christian

Computer engineer

David

Partner manager

Sofiene

Account manager

Kevin

Development Director

Samir

Chairman - Partner

Quentin

Computer engineer

Anthony

Outsourcing Manager

Amine

Computer technician

Laudine

Computer engineer

Yann

Computer engineer

Mathis

Developer

Mohamed

Account manager

Théo

Account manager

Olivier

Technical Manager

Julien

Computer engineer

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.

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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.

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How do you ensure the security of older, often vulnerable applications?

We strengthen security by adding encryption, modernizing authentication (MFA, SSO), implementing continuous monitoring and correcting critical vulnerabilities. We also ensure regulatory compliance, notably with RGPD and ISO 27001, to secure your data and processes.

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.