Strangler Pattern

Problem

How to modernize the complex legacy brownfield system without impacting client applications as completely replacing a complex system can be a huge undertaking?

You can think of a gradual migration to a new system by running of two separate versions of an application but it means that clients have to be informed where particular features are located.

Solution

Strangle Façade layer helps in replacing the complex legacy system with new system by creating a Strangler Façade layer between front end and back end system. Strangler façade layer will act as a single entry/exist point to client application and provides all the features using existing and new APIs without impacting the client.

This pattern may not be suitable:

When requests to the back-end system cannot be intercepted.
For smaller systems where the complexity of whole-replacement is low.