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Posted Apr 14, 2026

Senior API Developer Needed – Custom Private App Integration (WHOP → Funnelish)

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We are a fast-scaling ecommerce brand looking for a highly experienced API developer to build a custom private app that connects our payment gateway (WHOP) with Funnelish. Funnelish does not have a native integration with WHOP. We need someone who has handled complex payment gateway integrations before — not someone experimenting. This is not a junior project. We’re looking for a proven expert who has solved similar integrations successfully. We need a private app or middleware solution that: • Connects WOP payment processing to Funnelish • Properly passes order data to Funnelish • Correctly tracks initial purchases • Correctly tracks post-purchase upsells • Ensures tracking consistency (order value, customer data, transaction status) • Handles webhook logic reliably • Prevents duplicate or broken orders • Maintains accurate attribution and tracking inside Funnelish This must work cleanly for: • Main product checkout • One-click upsells • Post-purchase flows Tracking accuracy is critical. ⸻ Required Experience You must have: • Strong experience building private apps • Advanced experience with APIs and webhooks • Experience integrating payment gateways into third-party platforms • Experience working with ecommerce funnels • Deep understanding of order lifecycle, payment states, and tracking logic ⸻ This Is NOT for You If: • You are “learning as you go” • You are unsure whether this can be done • You have never handled custom payment integrations We are looking for someone confident and experienced. ⸻ To filter serious and qualified applicants, you MUST answer these questions clearly at the top of your proposal: 1. Have you ever done this exact type of integration (custom payment gateway → funnel builder)? If yes, explain briefly. 2. Have you done a similar integration involving custom APIs and payment webhooks? If yes, describe it. 3. Are you 100% confident you can complete this task successfully? Explain why. If you do not answer these 3 questions clearly, your application will not be considered.
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