docs: feature lifecycle (#7034)

website/docs/reference/feature-lifecycle.md

@@ -0,0 +1,61 @@
+---
+title: Feature Lifecycle
+---
+
+:::info Availability
+
+Feature lifecycle was introduced in Unleash 6.1.0
+
+:::
+
+![Feature Lifecycle example](/img/feature-lifecycle.png 'Feature Lifecycle example')
+
+Feature Lifecycle facilitates tracking the progression of features through various stages in their development and operational phases. 
+This systematic approach helps in identifying potential bottlenecks and improving the overall efficiency of the software development process.
+
+## Lifecycle stages
+
+Each stage in the lifecycle has a defined purpose:
+
+### Initial stage
+
+The feature flag is created but remains unseen in any environment.
+
+**Purpose:** marks the initiation of the feature.
+
+### Pre-live stage
+
+The feature flag has received metrics in non-production environment or has received metrics in a disabled production environment.
+
+**Purpose:** testing and validating the feature before it goes live. 
+
+### Live stage
+
+The feature has received metrics in the enabled production environment. 
+Once enough has been learned about the feature from production usage, you can mark the feature as completed.
+When marking a feature as complete, you decide whether to keep the feature, discard it, or keep one variant of the feature.
+This information can be used by code cleanup tools to automate feature removal from your code.
+
+**Purpose:** testing and validating the feature in production and marking feature completion.
+
+### Completed stage
+
+The feature's objectives have been achieved, and it is ready to be phased out.
+The lifecycle feature warns you if a completed feature continues to receive traffic, signaling that it hasn't been fully removed from the code.
+If you've accidentally marked the feature as completed, you can always revert it to the live stage.
+
+**Purpose:** initiating cleanup processes and signalling when it's safe to archive a feature.
+
+### Archived stage
+
+The feature is archived in Unleash and can be deleted. If an archived feature is revived, it starts a new lifecycle with a new initial stage. 
+
+**Purpose:** reducing technical debt by removing obsolete features.
+
+## Lifecycle stages and process improvement
+
+Understanding how much time a feature spends in each stage can highlight inefficiencies:
+* **Stuck in Initial**: May indicate integration issues in pre-production setups.
+* **Stuck in Pre-live**: Suggests challenges in achieving production readiness.
+* **Stuck in Live**: Could imply difficulties in data gathering or decision-making regarding the feature’s future.
+* **Stuck in Completed**: Indicates delays in decommissioning the feature and cleaning up resources.

website/sidebars.js

@@ -229,6 +229,7 @@ module.exports = {
                         'reference/event-log',
                         'reference/event-types',
                         'reference/feature-flag-naming-patterns',
+                        'reference/feature-lifecycle',
                         'reference/feature-toggles',
                         'reference/feature-toggle-types',
                         'reference/feature-toggle-variants',