A toggle is a simple switch with two outcomes (A or B). In general computing it is found when you have an options or preferences list that has option items that can be marked on and off.
Toggles can be a very effective user interface element, but they must be used carefully. They should always be clear to users about their state, use standard visual design conventions and deliver immediate results. Using toggles as a way to update settings or other kinds of information will often be a much better alternative than forms.
Many sites and apps use toggles to allow the user to change settings or preferences in a variety of ways. When done correctly they can make a huge difference to the user experience and be very effective at communicating complex actions. When not used correctly however they can be confusing, difficult to understand and even frustrating.
When Toggle Configuration is used in conjunction with a large number of service instances it is important to ensure that there is a consistent and predictable way to modify this configuration across all instances. This is why it is common to use some kind of centralized management mechanism for this type of data, usually built out of an existing application DB.
The best way to achieve this consistency is to have all toggles defined in one place and then be able to either load them into all the servers at once, or a subset of them with a single request. Toggle configurations can also be a key component of an experimentation or A/B testing platform where different variants of the same feature are deployed to a cohort of users. Then at runtime the Toggle Router will consistently send a given user down one codepath or another depending on the cohort they are in.
Toggle Configuration is a very powerful and effective tool but it can be dangerous when not used in a controlled environment where there are lots of other configuration settings being used on a shared server. This is why it is important to only use it for those things that will be stable for a long period of time and where there is a good way of managing the configuration via some kind of central management. Otherwise the system can become unstable, unreliable and difficult to manage at scale. This is why we recommend the use of a Champagne Brunch or Canary Release approach when working with feature toggles in production. This way a Canary Release version of a toggle can be tested at low risk to a small percentage of users before being moved into a Production Toggle. This will give the system operator confidence that a new feature is working well before it is deployed to the whole population of users. This will ensure a smooth rollout to the most valuable customers. This will also reduce the cost of experimenting with features and limit the impact of any regressions that may occur.
