A toggle is a binary control (on/off) that allows users to manage the state of content or a view. They are commonly used in web apps to enable or disable features.

Toggles are a great way to introduce new or experimental functionality but must be carefully designed to avoid confusing or misleading users. Toggles are not suitable for all use cases and other controls like radio buttons or checkboxes may be a better choice. In general, toggles should only be used as a control when the effect is immediate and can be applied without saving or any other input.

Toggle configuration is typically stored in some type of centralized store, usually an existing application DB. This can be a benefit as it removes the need for manual intervention to modify the toggle configuration. It also makes it easier to roll out a feature at scale by ensuring that only the toggle configuration currently in production is deployed.

One downside of this approach is that it can be difficult to verify how a toggle will perform in a live environment. This can be mitigated by deploying the toggle with a default value that is expected to produce the desired behavior. This helps to ensure that any change to the configuration will not negatively affect the user experience.

Another challenge with the toggle approach is that it can be hard to maintain clean code. As more and more toggles are introduced there is a risk that the code will become overly complex and difficult to read. To address this challenge many teams opt to move the toggle configuration out of source code and into a separate system where it can be easily managed.

For example, many organizations choose to store toggle configuration in a dedicated database which can be accessed by admins, testers and product managers. This can be a more stable and scalable solution but may require additional infrastructure to maintain.

In some cases it may make more sense to integrate the toggle configuration into a larger feature flag management system. This can provide a more flexible and easy-to-use interface for managing the feature flags that are deployed across a fleet of servers.

This is often necessary for enterprise applications where the feature flags need to be deployed to hundreds or even thousands of servers. Regardless of the approach, it is crucial that any toggle configuration is tested as it will be deployed to users in the real world. This should include testing the new feature with the toggle flipped Off and with a fallback toggle flipped On. It is also common for teams to test with all of the toggles that are planned for release flipped On to help prevent regressions in future releases. In addition, it is also wise to test any existing or legacy behavior with the toggle flipped Off as well. This will allow the team to verify that the feature is behaving as intended in a consistent way across all deployments.