Understand dark launching
Dark launching is in many ways like canary releases.
However, the difference here's that you're looking to assess users' responses to new features in your frontend rather than testing the performance of the backend.
The idea is that rather than launch a new feature for all users, you instead release it to a small set of users.
Usually, these users aren't aware they're being used as test users for the new feature, and often you don't even highlight the new feature to them, as such the term "Dark" launching.
Another example of dark launching is launching a new feature and using it on the backend to get metrics.
Let me illustrate with a real-world "launch" example.
As Elon Musk describes in his biography, they apply all kinds of Agile development principles in SpaceX.
SpaceX builds and launches rockets to launch satellites. SpaceX also uses dark launching.
When they have a new version of a sensor, they install it alongside the old one.
All data is measured and gathered both by the old and the new sensor.
Afterward, they compare the outcomes of both sensors.
Only when the new one has the same or improved results the old sensor is replaced.
The same concept can be applied to software. You run all data and calculations through your new feature, but it isn't "exposed" yet.
How to implement dark launching
In essence, dark launching doesn't differ from a canary release or the implementation and switching of a feature toggle.
The feature is released and only exposed at a particular time.
As such, the techniques, as described in the previous chapters, do also apply for dark launching.