Quick Reference
| Topic | File |
|---|
| ------- | ------ |
| Code traps that break production | code-traps.md |
| Platform comparison (costs, features) | platforms.md |
| Operations (stock, shipping, returns) | operations.md |
| Growth (CRO, upsells, LTV, benchmarks) | growth.md |
Critical Code Traps
These break production and cost real money. See code-traps.md for full patterns.
- Payment idempotency — Store
payment_intent_id, check before processing. Webhooks retry. - Inventory race conditions —
UPDATE ... WHERE stock > 0 with rowsAffected check, not read-then-write. - Frontend price trust — Backend recalculates everything. Never trust client totals.
- Webhook signatures — Verify
stripe-signature or equivalent. Reject unsigned requests. - Stock validation timing — Verify at payment moment, not just add-to-cart.
Core Rules
When Building Stores
- Calculate ALL prices server-side — discounts, shipping, taxes, totals
- Queue transactional emails — never inline in checkout flow
- Add structured data (Schema.org Product) and canonical URLs from day one
- Implement webhook signature verification before going live
When Operating Stores
- Monitor stock thresholds, not just zero — alert at reorder point
- Track orders stuck in "processing" >24h — detect before customer complains
- Log payment failures with context — card decline reasons matter for recovery
When Optimizing
- Checkout recovery: 1h, 24h, 72h sequence — discount on email 3, not 1
- Free shipping threshold: current AOV + 20-30%
- Mobile: sticky add-to-cart, Apple Pay/Google Pay, LCP <2.5s
Platform Decision Tree
- Budget <€500/mo, <100 SKUs: Shopify Basic or WooCommerce self-hosted
- Multi-marketplace: Dedicated sync tool (not manual updates)
- >1000 SKUs or ERP: WooCommerce/custom with PIM integration
For Spain-specific costs (IVA, OSS, carriers), see platforms.md.
Scope
This skill helps with:
- Store architecture and payment integration
- Inventory and order management logic
- Marketplace listing optimization
- Conversion rate tactics with benchmarks
- Legal/fiscal guidance for EU/Spain ecommerce
This skill does NOT:
- Connect to live store APIs (explain how, not execute)
- Store business data or credentials
- Make purchasing or pricing decisions autonomously