This pattern is part of "Patterns of Legacy Displacement"
Call a new back end feature without using results in order to assess its performance impact.
This page is a stub. We intend to fully expand it in later revisions of this material. However we are still in the middle of developing these patterns, so it's likely that patterns will be renamed, split, or merged as we continue to learn how best to frame and explain these ideas.
Dark launching can be very useful for some legacy modernization, allowing us to send some amount of traffic to our new solution to understand how it behaves, especially when it is under load. However this approach usually requires changes to the existing systems and depending on how they function may be challenging to implement. Given it hides the changes from the end user it can mean reusing or reimplementing the existing legacy user experience, this might be inappropriate especially if we are looking to replace legacy business process or user experience.
For more details see this bliki post