Project Detected: Node.js Express application --- Feature Flag Added: - Flag: checkout.new_flow.enabled - Controls: New checkout route and service - Default: Disabled --- Rollout Rules: - Enabled through the NEW_CHECKOUT_ENABLED environment variable - Existing checkout flow remains active when the flag is disabled or unavailable --- Implementation Summary: - Added a centralized feature flag service - Routed eligible requests to the new checkout flow - Preserved the existing checkout implementation as the fallback - Added tests for both flag states --- Files Modified: - src/config/featureFlags.js - src/routes/checkout.js - src/services/checkoutService.js - tests/checkoutFeatureFlag.test.js - .env.example --- Commands Executed: - npm test - npm run lint --- Validation Result: Tests and linting passed. The existing checkout flow is used by default, and the new flow activates only when the flag is enabled. --- How to Test: Set NEW_CHECKOUT_ENABLED=true locally, restart the app, and run npm test. Set it to false to verify the existing checkout flow. --- Important Notes: This flag does not replace payment authorization or validation. Remove the flag after the new checkout flow is fully released and stable.