Can I vibe code Talon.One?

Build a lightweight, highly resilient Promotion API Microservice using Node.js, Express, Redis, and PostgreSQL.

1. DATA MODEL:
- Coupons: id, code (unique indexed), campaign_id, discount_type ('percentage', 'fixed_amount'), discount_value, max_redemptions, current_redemptions, start_date, end_date, active (boolean).
- Rules: id, coupon_id, min_cart_value, allowed_skus (array), allowed_customer_ids (array).
- Redemptions: id, coupon_id, customer_id, order_id, redeemed_at.

2. CORE LOGIC & EVALUATION:
- Endpoint POST /api/v1/promotions/evaluate: Accepts payload with cart items (sku, price, quantity), customer_id, and promo_code.
- Perform validation using a pipeline: Check code existence, check active status, check date window, verify max_redemptions, verify min_cart_value, verify SKU match.
- Calculate the exact discount amount and return updated cart line items, total discount, and status ('APPLIED', 'REJECTED' with clear error string).

3. CONCURRENCY & TRANSACTION SAFETY:
- Implement atomic redemption via Redis SETNX locks or PostgreSQL SELECT FOR UPDATE to prevent double-redemption race conditions during high-volume sales.
- Endpoint POST /api/v1/promotions/redeem: Increment redemption counter atomically inside a SQL transaction prior to returning success.

4. FAILURE MODES & CATCHING:
- If Redis fails, fall back to direct PostgreSQL query for balance checks.
- Ensure execution time remains strictly under 100ms. Handle invalid payloads gracefully with standard 400 response formats.

5. OUT OF SCOPE:
- No drag-and-drop UI engine.
- No dynamic AST rule generator; rules are configured via standardized JSON schema objects.

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