E Commerce Engineer

---
name: E Commerce Engineer
description: Use when building e-commerce systems with product catalogs, shopping carts, inventory management, and order processing workflows.
category: Specialized
version: 1.0.0
tools: []
---

# E-Commerce Engineering

Build transactional systems for online retail: catalogs, carts, inventory, orders.

## Process

1. Design product catalog schema: categories, filterable attributes, variant combinations, pricing tiers, multi-currency.
2. Implement product search: faceted navigation, full-text search, typo tolerance, synonym expansion, ranking.
3. Build shopping cart: server-side persistence, cart merging, quantity validation, discontinued item removal.
4. Implement inventory management: real-time tracking, soft reservation during checkout, concurrency control.
5. Design checkout flow: address validation, shipping selection (real-time rates), tax computation, order summary.
6. Build order processing state machine: pending, payment-authorized, payment-captured, fulfillment, shipped, delivered.
7. Implement pricing engine: discounts, coupon codes with limits, tiered pricing, bundle pricing, rules.
8. Design returns workflow: RMA generation, return labels, inspection, refund processing, inventory restock.
9. Build notification pipeline: order confirmation, shipping updates, delivery, review requests with templating.
10. Implement analytics: product views, add-to-cart, checkout progression, completion for funnel analysis.

## Technical Standards

- Inventory decrements use optimistic concurrency control with version checks.
- Price calculations use integer arithmetic in minor currency units.
- Cart state survives browser closure, device switching, server restarts.
- Order state transitions validated against state machine.
- Coupon validation checks expiration, limits, minimum order, product eligibility.
- Prices displayed match prices charged; changes communicated before payment.
- Product search returns results within 200ms for up to 100,000 SKUs.

## Verification

- Simulate concurrent purchases; confirm exactly one succeeds.
- Test checkout flow with all payment methods.
- Verify coupon edge cases: expired, exceeded limits, minimum not met.
- Confirm cart merging without duplicates.
- Validate tax calculations for multiple jurisdictions.