eBay OAuth & Webhook Integration Developer (Replit App)

Overview:

We need an experienced developer to fix our broken eBay OAuth 2.0 flow, set up all eBay webhooks, and fully integrate every available API category into our Replit-based business app.

Immediate Issues:
• OAuth callback fails with HTTPS/cert errors (Replit redirect domains broken).
• Token refresh and client credential grant are unreliable.
• The “Test Sign-In” button in eBay’s Dev Portal is non-functional and must be diagnosed.
• Notifications API (webhooks) not configured or wired to the app.
• eBay API categories (orders, inventory, returns, messaging, etc.) are only partially implemented.

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Core Responsibilities:
• Fully repair OAuth login + token refresh for multi-user consent.
• Resolve redirect URI and SSL/cert conflicts using custom domains or reverse proxies.
• Register and handle every available webhook (e.g., ITEM_REVISED, ORDER_SHIPPED, RETURN_CREATED, etc.).
• Ensure webhook payloads are verified and synced to our Replit/PostgreSQL backend.
• Integrate every eBay API scope/category into the app (Orders, Messages, Listings, Returns, Cases, Promotions, etc.).
• Diagnose and fix broken “Test Sign-In” window in the eBay Dev Portal.

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Requirements:
• Strong experience with OAuth 2.0 (esp. eBay’s implementation).
• Solid knowledge of Express, Node.js (TypeScript), PostgreSQL, and REST APIs.
• Familiarity with Replit environments and workarounds for HTTPS or domain issues.
• Experience implementing and securing webhook endpoints.

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Optional but Helpful:
• Shopify/USPS API experience
• Retry queues for failed webhook delivery
• UI integration for logs, token status, or session control

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Type:
• Freelance/contract
• Paid upon successful fix + delivery confirmation

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To Apply:

Send:
• Short explanation of how you’d solve the OAuth and webhook issues
• Relevant portfolio/github