eBay Marketplace API Integration
Production-ready listing management system using eBay's modern Sell APIs (Inventory, Account, Fulfillment) with OAuth 2.0, business policies, and async processing for scalable marketplace integration.
Feature Overview
Core capabilities and future enhancements for eBay Sell API integration
Must-Have (MVP)
- OAuth 2.0 authentication (Auth Code + Client Credentials grant)
- Business policy setup (fulfillment, return, payment policies)
- Inventory item creation/update (SKU management)
- Offer creation with marketplace + policies
- Publish offer flow (inventory → offer → live listing)
- Async job queue with retry and DLQ
- Token vault with refresh token encryption (KMS/Secrets Manager)
- Error normalization and throttle handling
Nice-to-Have (Later)
- Multi-seller platform support
- Bulk listing operations
- Order management (Fulfillment API integration)
- Shipping fulfillment + tracking updates
- Category/aspect validation engine
- Listing revision tracking (250/day limit monitoring)
- Seller performance dashboard
- Webhook notifications for orders
System Architecture
Multi-layered architecture for secure, scalable eBay marketplace integration
Presentation Layer
Seller/Admin UI for listing creation, publishing, and status monitoring
- React Dashboard
- Draft Editor
- Status View
- Error Display
Application Layer
Backend services orchestrating eBay API calls and business logic
- Listing Draft Service
- Media Service
- eBay Integration Service
- Webhook Handler
Data Layer
Persistent storage for sellers, tokens, inventory, offers, and audit logs
- SellerAccount + OAuth Tokens
- InventoryItem (SKU-based)
- Offer + PublishAttempt
- Object Store (images)
Security Layer
OAuth 2.0 authentication with encrypted token storage and access control
- OAuth Auth Code Grant
- Token Vault (KMS encrypted)
- Scope Management
- Audit Logging
Publishing Flow
End-to-end workflow from seller setup to live eBay listing using Sell Inventory API
Step 0: Seller Setup (One-time)
- Seller connects account via OAuth Auth Code grant
- Ensure seller opts into Business Policies
- Create/assign fulfillment, return, and payment policies (required)
Step 1: Create Inventory Item (SKU)
- Save local draft with title, description, images, aspects
- Worker calls Inventory API to create/update SKU
- Store SKU and eBay inventory item response
Step 2: Create/Update Offer
- Call createOffer with marketplace + SKU + policies
- Set price, quantity, category, listing duration
- Update offer as needed (updateOffer)
Step 3: Publish Offer (Go Live)
- Call publishOffer(offerId) to create live listing
- Persist listing ID and status
- Monitor revision limits (250 revisions/day per listing)
Step 4: Revise / End Listing
- Revise by updating offer + republishing
- End listing via withdraw/delete offer
- Track all operations in PublishAttempt audit log
Security & Reliability
Production-grade security controls for OAuth, token management, and error handling
OAuth 2.0 Authentication
Auth Code Grant for seller-connected apps with user access tokens and refresh token management
- Secure authorization code exchange
- Refresh token rotation
- Scope-based access control
- Token expiration handling
Token Vault Security
Encrypted storage for refresh tokens using KMS or cloud secrets manager
- Encrypted at rest (KMS/Key Vault/Secrets Manager)
- Never expose tokens to frontend
- Least privilege scope requirements
- Automatic secret rotation
Retry & Throttling
Resilient API call handling with exponential backoff and rate limiting
- Exponential backoff + jitter for transient failures
- Per-seller and per-API rate limiting
- DLQ for manual review of failures
- Idempotency keys to prevent duplicates
Error Handling
Comprehensive error normalization and validation before submission
- Business policy validation (fulfillment/return/payment)
- Category and aspect validation
- Missing data detection
- Structured error logging with correlation IDs
Key Benefits
Why choose this eBay Marketplace API integration architecture
Modern API Stack
Built on eBay's recommended Sell Inventory API (not legacy Trading API) for create, update, and publish operations
Secure OAuth 2.0
Auth Code Grant with encrypted refresh token storage and automatic rotation for production-grade security
Multi-Seller Ready
Designed for platforms managing listings across multiple seller accounts with proper token isolation
Scalable Async Processing
Queue-based architecture with retry logic, DLQ, and throttle handling for reliable high-volume listing management
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