Basic Feature Flags

Learn how to use simple on/off feature toggles with FlagVault SDK

Cached vs Real-time Flag Evaluation

Compare how caching affects flag response behavior

The cached flags use HTTP cache headers and SDK cache, while real-time flags bypass caching for immediate updates

Cached Flags

5 min TTL

These flags are cached: Changes in your dashboard may take up to 5 minutes to reflect here. This improves performance but reduces real-time accuracy.

demo-feature

SDK not initialized

beta-features

SDK not initialized

Real-time Flags

No Cache

These flags update immediately: Changes in your dashboard will reflect within seconds. This provides real-time accuracy but may be slower.

new-ui-design

Checking...

maintenance-mode

Checking...

When to Use Each Strategy

✅ Use Cached Flags For:

• High-traffic features
• Performance-critical code paths
• Features that don't need instant updates
• Reduced API costs

⚡ Use Real-time Flags For:

• Emergency kill switches
• Security-related features
• Critical user-facing changes
• A/B test result accuracy

Custom Flag Check

Enter your own flag key to check its status

Implementation Examples

Code snippets showing how to implement cached vs real-time flag evaluation

Cached Flag Evaluation (Recommended)

import FlagVaultSDK from '@flagvault/sdk';

// SDK with caching enabled (recommended for most use cases)
const sdk = new FlagVaultSDK({
  apiKey: 'test_your-api-key-here',
  cache: {
    enabled: true,
    ttl: 300, // 5 minutes cache
    maxSize: 1000,
    refreshInterval: 60 // 1 minute background refresh
  }
});

// Cached flag evaluation - fast but may be slightly stale
const isEnabled = await sdk.isEnabled('demo-feature');

if (isEnabled) {
  showNewFeature();
} else {
  showOldFeature();
}

Real-time Flag Evaluation (Critical Features)

import FlagVaultSDK from '@flagvault/sdk';

// SDK with minimal caching for real-time updates
const realtimeSdk = new FlagVaultSDK({
  apiKey: 'test_your-api-key-here',
  cache: {
    enabled: false // Disable cache for immediate updates
  }
});

// Real-time flag evaluation - slower but always current
const isMaintenanceMode = await realtimeSdk.isEnabled('maintenance-mode');

if (isMaintenanceMode) {
  showMaintenancePage();
} else {
  showNormalApplication();
}

Graceful Error Handling

// No try/catch needed - errors are handled gracefully
const isEnabled = await sdk.isEnabled('my-feature-flag', false);

// On network error, you'll see:
// FlagVault: Failed to connect to API for flag 'my-feature-flag', using default: false

// On authentication error:
// FlagVault: Invalid API credentials for flag 'my-feature-flag', using default: false

// On missing flag:
// FlagVault: Flag 'my-feature-flag' not found, using default: false

How It Works

Understanding the feature flag lifecycle

1SDK makes a GET request to https://api.flagvault.com/api/feature-flag/{flag-key}/enabled
2API validates your credentials and checks the flag status in the selected environment
3Returns a boolean value indicating if the flag is enabled
4On error, returns the default value you specified (graceful degradation)