Lesson263 words
Feature flags with Azure App Configuration
Implement feature flags by using Azure App Configuration Feature Manager
The vocabulary the docs define
- Feature flag — a variable with a binary state, on or off, with an associated code block. The flag's state decides whether that block runs.
- Feature manager — an application package that handles the lifecycle of all flags in the application, including caching flags and updating their states.
- Feature filter — a rule that decides whether a flag is on for this request: percentage, time window, targeted audience.
Why it belongs in App Configuration
Storing flags centrally means one place to change behaviour across every instance and service, rather than a config file per deployment. The application reads flag state at runtime, so feature availability changes without redeploying code.
The five documented use cases
| Use case | What it enables |
|---|---|
| Code branch management | Dark deployment — ship unfinished features dormant, avoid long-lived branches |
| Test in production | Real production fidelity for internal users or beta testers |
| Flighting | Incremental rollout to a growing percentage |
| Instant kill switch | Disable without rebuild or redeploy |
| Selective activation | Segment users — e.g. one browser only |
Operational care
Because the feature manager caches flag state, a change is not necessarily instantaneous — know your refresh interval before promising a kill switch acts in seconds. And flags accumulate: a flag whose rollout finished is dead code plus a branch that is no longer tested. Retire them.
Primary sources