Feature Flags

Overview

Feature flags separate deploy from release. Deploy puts code on the server (applad deploy). Release makes functionality live to users (feature flags). These are independent decisions made by different people at different times.

How Flags Work

Flag skeletons — that a flag exists, its variants, its per-environment defaults — live in flags/*.yaml and are version controlled. Targeting rules (which users see which variant) live in the admin database and are managed through the UI without a deployment.

┌─────────────────────┐
│   flags/*.yaml      │  ← Version controlled
│   • Flag exists     │
│   • Type & variants │
│   • Env defaults    │
└─────────────────────┘

┌─────────────────────┐
│   Admin Database    │  ← Managed via UI
│   • Targeting rules │
│   • User segments   │
│   • % rollouts      │
└─────────────────────┘

Flag Types

Boolean Flags

Simple on/off switches:

flags/new-dashboard.yaml

key: "new-dashboard"
type: "boolean"
default: false
description: "New dashboard UI redesign"

environments:
  development: true
  staging: true
  production: false

Multivariate Flags

A/B tests with multiple variants:

flags/checkout-flow.yaml

key: "checkout-flow"
type: "multivariate"
default: "control"
variants: ["control", "variant-a", "variant-b"]
description: "A/B test for checkout flow"

environments:
  development: "variant-a"
  staging: "control"
  production: "control"

Creating Flags

Generate flag skeleton

applad flags generate new-feature

Creates flags/new-feature.yaml with default structure.

Configure flag type and defaults

flags/new-feature.yaml

key: "new-feature"
type: "boolean"
default: false
description: "New feature release"

environments:
  development: true   # Enabled in dev
  staging: true       # Enabled in staging
  production: false   # Disabled in production

Deploy the flag skeleton

applad up --dry-run --diff
applad up

The flag now exists but is off in production.

Configure targeting in admin UI

Open the admin UI and navigate to Flags > new-feature. Configure:

User segments (beta users, internal team, specific orgs)
Percentage rollouts (5%, 25%, 50%, 100%)
Custom targeting rules

Changes take effect immediately — no deployment required.

Environment Defaults

Set per-environment defaults in the YAML file:

flags/experimental-feature.yaml

environments:
  development: true   # Always on in dev
  staging: true       # Always on in staging
  production: false   # Off by default in production, controlled via targeting

Using Flags in Code

Applad provides SDKs for all major platforms:

Dart/Flutter

import 'package:applad/applad.dart';

// Boolean flag
final showNewDashboard = await applad.flags.isEnabled('new-dashboard');

if (showNewDashboard) {
  return NewDashboard();
} else {
  return OldDashboard();
}

// Multivariate flag
final variant = await applad.flags.getVariant('checkout-flow');

switch (variant) {
  case 'variant-a':
    return CheckoutFlowA();
  case 'variant-b':
    return CheckoutFlowB();
  default:
    return CheckoutFlowControl();
}

JavaScript/TypeScript

import { applad } from '@applad/sdk';

// Boolean flag
const showNewDashboard = await applad.flags.isEnabled('new-dashboard');

if (showNewDashboard) {
  renderNewDashboard();
} else {
  renderOldDashboard();
}

// Multivariate flag
const variant = await applad.flags.getVariant('checkout-flow');

if (variant === 'variant-a') {
  renderCheckoutA();
} else if (variant === 'variant-b') {
  renderCheckoutB();
} else {
  renderCheckoutControl();
}

Managing Flags

List all flags

applad flags list

Shows type, per-environment defaults, and whether targeting rules are configured.

Validate flag definitions

applad flags validate

Checks syntax, that multivariate flags have at least two variants, and that defaults are valid variants.

View flag details

applad flags show new-dashboard

Shows full definition, per-environment defaults, and current targeting rules.

Enable/disable flags

# Enable for environment
applad flags enable new-dashboard --env production

# Disable for environment
applad flags disable new-dashboard --env production

Updates the admin database. Takes effect immediately without deployment.

View evaluation logs

applad flags logs new-dashboard

Shows every evaluation — when the flag was checked, which variant was returned, and for which user.

Gradual Rollouts

Instead of flipping a flag on/off instantly, roll it out gradually:

Deploy code with flag off in production
In admin UI, set flag to 5% of users
Monitor metrics
Increase to 25%, then 50%, then 100%
Flag is now fully released

If issues are detected at any stage, immediately set back to 0% without redeploying.

User Segmentation

Target flags to specific user groups:

Beta users — Users who opted into beta features
Internal team — Your company email domain
Specific orgs — Enterprise customers, specific tenants
User properties — Country, plan level, signup date

Configured entirely through the admin UI.

Dark Launches

Deploy code to production with flags off, then enable for internal testing:

Deploy with production: false in flag YAML
Code is on production servers but inactive
In admin UI, enable flag only for internal team
Test feature in production environment with real data
When confident, enable for all users

No separate staging environment needed. Test in production safely.

Instant Rollbacks

If a released feature causes problems:

applad flags disable new-feature --env production

Or through admin UI: set flag to 0% of users. Takes effect immediately. No deployment, no rollback, no downtime.

Flag Lifecycle

Created — Flag skeleton committed to version control
Deployed — Flag exists, default is off
Testing — Enabled for internal team only
Canary — Enabled for 5-10% of users
Rollout — Gradually increased to 100%
Released — Fully enabled for all users
Cleanup — Remove flag from code and config after feature is stable

Best Practices

One flag per feature

Don’t reuse flags for multiple features. Each feature gets its own flag with a clear, descriptive name.

Clean up old flags

Once a feature is fully released and stable, remove the flag from code and delete the YAML file. Flags are temporary release controls, not permanent configuration.

Use descriptive keys

Flag keys should describe what the flag controls:

new-checkout-flow ✓
experiment-42 ✗

Document flag purpose

Always include a description field explaining what the flag controls and why it exists.

Default to off in production

Production environment should default to false for boolean flags and "control" for multivariate flags. Release is an active decision.

Example: A/B Test Configuration

flags/pricing-page-redesign.yaml

key: "pricing-page-redesign"
type: "multivariate"
default: "control"
variants: ["control", "variant-a", "variant-b", "variant-c"]
description: "A/B test for pricing page layout and copy"

environments:
  development: "variant-a"  # Always show variant-a in dev
  staging: "control"        # Default to control in staging
  production: "control"     # Default to control in production

In admin UI:

Control: 70% of users
Variant A: 10% of users
Variant B: 10% of users
Variant C: 10% of users

Monitor conversion rates. Once a winner is identified, set 100% to that variant. After stable for 2 weeks, remove flag and make variant the default code path.

Example: Dark Launch

flags/new-analytics-engine.yaml

key: "new-analytics-engine"
type: "boolean"
default: false
description: "New analytics processing engine"

environments:
  development: true
  staging: true
  production: false  # Deployed but inactive

Deploy to production. In admin UI, enable only for:

Internal team members
Beta users who opted in

Test with real production data and traffic. When confident, gradually roll out to all users.

Getting Started

Core Concepts

Configuration

Guides

Deployment

Overview

How Flags Work

Flag Types

Boolean Flags

Multivariate Flags

Creating Flags

Environment Defaults

Using Flags in Code

Dart/Flutter

JavaScript/TypeScript

Managing Flags

List all flags

Validate flag definitions

View flag details

Enable/disable flags

View evaluation logs

Gradual Rollouts

User Segmentation

Dark Launches

Instant Rollbacks

Flag Lifecycle

Best Practices

Example: A/B Test Configuration

Example: Dark Launch

Next Steps

Messaging

AI Assistant

Build docs developers (and LLMs) love

Getting Started

Core Concepts

Configuration

Guides

Deployment

​Overview

​How Flags Work

​Flag Types

​Boolean Flags

​Multivariate Flags

​Creating Flags

​Environment Defaults

​Using Flags in Code

​Dart/Flutter

​JavaScript/TypeScript

​Managing Flags

​List all flags

​Validate flag definitions

​View flag details

​Enable/disable flags

​View evaluation logs

​Gradual Rollouts

​User Segmentation

​Dark Launches

​Instant Rollbacks

​Flag Lifecycle

​Best Practices

​Example: A/B Test Configuration

​Example: Dark Launch

​Next Steps

Messaging

AI Assistant

Build docs developers (and LLMs) love

Overview

How Flags Work

Flag Types

Boolean Flags

Multivariate Flags

Creating Flags

Environment Defaults

Using Flags in Code

Dart/Flutter

JavaScript/TypeScript

Managing Flags

List all flags

Validate flag definitions

View flag details

Enable/disable flags

View evaluation logs

Gradual Rollouts

User Segmentation

Dark Launches

Instant Rollbacks

Flag Lifecycle

Best Practices

Example: A/B Test Configuration

Example: Dark Launch

Next Steps