Feature Toggling

What?

• Ability to toggle features for user subset
• For all/some users
• Eg. Chat

Why?

• Ease in users to new features
• A/B testing
• Dynamically switch features
  without releases
• Gauge key user metrics
• Less branching
• Safe to fail

How?

• Account level flag (+ opt-in)
• Market level flag (+ opt-in)
• Universal + opt-in

Account level flag
(+ opt-in)?

• Choose a random subset of 1% of users
• Set a featureEnabled flag on User Accounts
• Check for flag on client and enable/disable feature
• Use flag in Snowplow/GA for A/B testing

What is opt-in?

• Eligible users opt-in to try out feature
• No forcing features down users' throats
• Additional featureOpted flag set from Client

• Only featureEnabled + featureOpted enables feature

Implementation

• Client implements feature toggling framework
• Backend makes schema changes
• Business decides key user metrics (engagement, revenue etc.)
• Client & backend implement analytics
• Plug and play
• Optionally, Admin implements feature toggling

Advantages

• Client agnostic (Web/Android/iOS)
• Market agnostic
• Safe
• Controlled number of users
• Opt-in:
  • Great UX

Market level flag (+opt-in)

• All users of a selected market
• Can be tried out in low traffic markets

Advantages

• Only one market will be affected if something breaks
• Mass use metrics will be available

Disadvantages

• Large uncontrolled number of users
• Market specific metrics won't be available
  in analytics

Universal + opt-in

• All users are eligible by default
• Users can opt-in
• Similar to Account level flag
• Onus lies on user

Advantages

• Pan market/client use
• Close to real use data

Disadvantages

• Number of users can grow out of control
• Might annoy large numbers of users

Bonus feature

• Adds implementation cost

Bonus feature

• Adds implementation cost

Additional reading

• http://martinfowler.com/articles/feature-toggles.html
• http://swreflections.blogspot.in/2014/08/feature-toggles-are-one-of-worst-kinds.html
• https://abhishek-tiwari.com/post/decoupling-deployment-and-release-feature-toggles
• https://www.rallydev.com/blog/engineering/awesomeness-feature-toggles