API Integration Design & Error Handling Architect

Design an API integration between Shopify paid orders and our ERP. Context: - Shopify is the source of truth for order creation and payment status. - The ERP is used for fulfillment and accounting. - We need to sync paid orders, customers, line items, shipping address, tax, currency, and payment status. - We are worried about duplicate orders, webhook retries, missing SKU mappings, ERP timeouts, rate limits, and partial failures. Please include: - integration architecture - data contract - field mapping approach - request validation - response validation - retry and backoff policy - idempotency strategy - rate-limit protection - dead-letter handling - monitoring and alerting - testing matrix - runbook notes

=== API INTEGRATION DESIGN & ERROR HANDLING BLUEPRINT === Business process: Sync paid Shopify orders into the ERP for fulfillment and accounting. Systems integrated: - Source: Shopify - Target: ERP Source of truth: Shopify is the source of truth for order creation and payment status. The ERP is the source of truth for fulfillment and accounting processing after successful sync. Integration architecture: 1. Shopify order-paid webhook. 2. Webhook signature validation. 3. Event ID capture. 4. Payload validation. 5. Order transformation. 6. ERP customer lookup or create. 7. ERP order create. 8. Idempotency and state store. 9. Dead-letter handling. 10. Monitoring and reconciliation report. Data contract: Required source fields: - Shopify order ID - customer ID or customer email - line items - variant IDs or SKUs - quantity - price - currency - payment status - shipping address Required target fields: - ERP customer reference - ERP order lines - ERP item ID or SKU - quantity - price - tax - shipping method - payment status Request validation: Reject or route to review if: - Shopify order ID is missing - payment status is not paid - line items are empty - SKU mapping is missing - currency is unsupported - shipping address is incomplete - tax mapping cannot be determined Response validation: Confirm that: - ERP customer reference is returned - ERP order ID is returned - order status is accepted or created - line item count matches expected count - no partial success warning is present Idempotency strategy: Use Shopify order ID plus operation type as the idempotency key. Duplicate behavior: If the ERP order already exists, do not create another order. Update sync status and append an audit note. Retry policy: Retry timeouts, 429 responses, and selected 5xx responses with exponential backoff and jitter. Do not retry validation failures, missing SKU mappings, permission errors, or malformed requests. Rate-limit protection: Queue order sync jobs and throttle ERP requests according to provider limits. Alert if queue depth grows or repeated rate-limit responses occur. Dead-letter handling: Route failed orders to a review queue with: - Shopify order ID - correlation ID - failed step - error category - safe error message - retry count - recommended action - replay allowed flag Monitoring: Track: - orders received - orders synced - orders failed - duplicate orders prevented - retry count - ERP latency - dead-letter count - SKU mapping failures - reconciliation mismatches Testing matrix: - valid paid order - missing SKU mapping - unsupported currency - duplicate webhook event - ERP timeout before response - ERP timeout after accepting request - ERP validation error - rate-limit response - partial customer created but order failed - replay from dead-letter - reconciliation report detects unsynced paid order Runbook notes: - integration owner must review dead-letter items daily during pilot - failed SKU mappings should be assigned to operations or catalog owner - replay is allowed only after idempotency key and ERP order status are checked - production rollout should begin with a limited-volume pilot