Modernizing Legacy Software: Strategies and Best Practices [2026]

Legacy systems are the backbone of many companies – and at the same time their biggest technical challenge. These often decades-old systems contain valuable business logic and critical data, but are difficult to wait, expensive to operate and an obstacle to innovation. Modernization is inevitable, but how do you really do it?

Why legacy moderation is inevitable

EffectivenessRisk

Outdated technologyNo updates, vulnerabilitiesHigh Lack of expertiseNiemand understands the system moreCritical High maintenance costsUp to 80% of the IT budget Integration problemsNo APIs, no cloud capabilityHigh Compliance Risk DSGVO, Security StandardsCritical

The four modernization strategies

1. Rehosting ("Lift and Shift")

The application is moved into a new environment (e.g. cloud) without any changes.

advantages

• Fast implementable
• Low risk
• Low cost

disadvantages

• No real modernization
• Problems remain

2. [Refactoring](/performance/software recovery)

The existing code is gradually improved without changing functionality.

advantages

• Get business logic
• Stepwise procedure possible
• Lower risk as new development

disadvantages

• Time-consuming
• Requires deep system understanding

3. Rearchitecting

The application is converted into a modern architecture (e.g. microservices).

advantages

• Real modernization
• Better scalability
• Future-proof

disadvantages

• High effort
• Complex migration

4. Replacement

The legacy system is replaced by a new solution (own development or standard software).

advantages

• Clean new beginning
• Modern technology

disadvantages

• Maximum risk
• Loss of business logic
• Long project duration

Best Practices for Modernization

• Be aware of the system: Document the existing functionality before you change.

• Define clear targets: What should modernisation achieve?

• Progress: Avoid Big Bang migrations.

• Test thoroughly: Automated tests are indispensable.

• Plan data migration: Data are often the most critical part.

• Should your team: New technologies require new skills.

"The best modernization strategy is that you can actually implement – not the theoretically perfect one."

Conclusion: Modernization is a marathon, not a sprint

The modernization of legacy software is one of the most demanding tasks in IT. It requires technical know-how, strategic thinking and a lot of patience. But the alternative – an outdated system that eventually collapses – is not an option. With the right strategy and professional support, modernization is feasible.

Are you fighting with legacy systems?

We help you find and implement the right modernization strategy. Consulting anfo