Stepwise migration: The Strangler-FIG-Pattern for the modernization of old systems

Step by step Migration: The Strangler-Fig-Pattern to Modernize Old Systems

In today's fast-paced digital landscape, many companies face the challenge of modernizing outdated IT systems. These so-called old systems are often the backbone of the company.

However, their rigid architectures and outdated technologies hinder innovation and growth. A complete new development is often associated with high costs, risks and long development times.

Here, the Altsystem Migration with the Strangler-Fig-Pattern offers an elegant and low-risk alternative.

What is the Strangler-FIG-Pattern?

In today's fast-paced digital landscape, many companies face the challenge of modernizing outdated IT systems.

When planning Stepwise migration: The Strangler-FIG-Pattern for the modernization of… from idea to delivery, Legacy Modernisation, Cost Calculator: Legacy Modernisation, Solution: Legacy Reduction sowie Monolith vs. Microservices offer practical next steps on our site.

The Strangler-Fig-Pattern, in German “Würgefeigen-Muster”, is an architectural pattern made popular by Martin Fowler.

The name derives from the wortfeige, a plant that grows on another tree, slowly wraps it around and finally completely replaces it.

Transfer to software development this means replacing an old system step by step with a new system by gradually implementing the features of the old system in new services and slowly “worn” access to the old system.

Instead of a risky “Big Bang” migration, in which the entire system is replaced at once, the Strangler-Fig-Pattern allows incremental modernization.

A new system is built parallel to the old one and custom functionalities are gradually migrated from the old system into the new system.

A façade, often in the form of a proxy or API gateway, passes the queries either to the new system or to the old system.

Over time, the new system takes over more and more tasks until the old system can be completely replaced and shut down.

The advantages of gradual migration

The use of the Strangler-FIG-Pattern in the Altsystem Migration offers a number of decisive benefits:

• Risk minimisation: As migration takes place in small, manageable steps, the risks are drastically reduced compared to a complete new development. Errors and problems can be detected and resolved at an early stage without endangering the entire system.
• Continuous value added: New functionalities and improvements can be quickly switched on, which means that the company steadily benefits from modernization and does not have to wait years for the result. *Slower downtime: Migration can be carried out during operation without long downtime. This is crucial especially for business-critical applications.
• Room to adapt: The development team can use modern technologies and architectures for the new system without being bound to the limitations of the old system. This allows the introduction of microservices, cloud-native technologies and agile development.

References and further reading

The following separate references complement the topics in this article:

• Bitkom – German digital industry association.
• German Federal Office for Information Security (BSI).
• European Commission – Digital strategy.
• MDN Web Docs (Mozilla)
• W3C – World Wide Web Consortium.

"DevOps is less about tools and more about shared ownership of quality and release discipline."

— Björn Groenewold, Managing Director, Groenewold IT Solutions

Frequently Asked Questions (FAQ)

What is this article about: “Stepwise migration: The Strangler-FIG-Pattern for the modernization of old systems”?

This post explores Stepwise migration. The Strangler-FIG-Pattern for the modernization of old systems from the perspective of needs, typical pitfalls. And sensible next steps. In short.

In today's fast-paced digital landscape, many companies face the challenge of modernizing outdated IT systems. These so-called old systems are often the backbone of the...

Who benefits most from the content described here?

Useful for project leads and product owners in Software development who must choose between standard software, custom development, and integration.

How does this topic fit into an IT or digital strategy?

Technically and organizationally, alignment with experienced partners pays off — from requirements to operations; start with the [services overview](/en/services/software-development). For multi-system landscapes, [IT consulting and architecture](/en/services/it-consulting) helps align vendors and internal teams.

What are sensible next steps if we need support?

A practical next step: book a consultation and clarify which MVP or pilot fits your team and landscape.