Senior WordPress Plugin Developer — Stripe Connect Express Marketplace (Fixed Price)

About the Project: We're hiring a senior WordPress plugin developer to build a custom Stripe Connect Express marketplace payment plugin for an existing WordPress + WPJobster site. The plugin handles the full payment lifecycle for a marketplace selling pre-recorded service sessions: buyer checkout via Stripe Checkout, destination charges with platform fee separation, 30-day payout holds, multi-jurisdiction tax via Stripe Tax with a 9-setting multi-code architecture, audit-grade financial recordkeeping for EU and US compliance, and an independent third-party code audit at the final milestone. The plugin is 19 custom DB tables, 13 admin settings groups, four PDF document types (three invoice variants + buyer receipt), 47 editable email templates, and 22 conflict tests across five milestones. The full developer briefing is approximately 860 KB and is shared only after a paid live working session confirms technical fit (more on this below). Platform Stack: - WordPress 6.7+ with WPJobster theme as the marketplace foundation - PHP 8.1+ / MySQL 8.0+ - 19 custom DB tables (not WordPress post types) - Stripe Connect Express (destination charges, manual transfers, 30-day payout hold) - Stripe Checkout (hosted) with embedded payment_intent_data for marketplace flows - Stripe Tax with multi-jurisdiction architecture (9 admin settings; CPA-confirmed product codes) - AWS SDK for PHP for S3 document storage (~38,000 PDFs/year at 100 sellers, ~384,000 over 10-year EU retention) - Composer for dependency management; PHPUnit for test coverage - Standard WordPress hooks, cron, admin UI conventions What You'll Build (5 Milestones): - **M1 — Foundation:** Plugin skeleton, all 19 DB tables, full 13-group admin settings panel, dependency check, integration verification with Jobster - **M2 — Payment Flow:** Sessions via Stripe Checkout with destination charges, platform fee separation, 30-day payout hold state machine - **M3 — Tax & Documents:** Stripe Tax integration, four PDF document types with proper VAT legal text, multi-jurisdiction handling - **M4 — Tips, Featured Jobs, Refunds:** Additional payment flows, refund routine with edge cases - **M5 — Hardening & Audit:** Security audit report, integration verification, PHPUnit test suite, **independent third-party code audit** (we hire this auditor independently of you) Hiring Process — Verification Built In: We use a multi-stage flow designed to filter for actual individual technical capability: 1. **Application screening** — your application + 5 screening questions 2. **Vertical disclosure (written)** — we share the business vertical so you can opt out cleanly if it's not a fit for you, before any time investment 3. **Pre-NDA Zoom (~30 min)** — fit check (NOT a technical interview) 4. **Scope Summary delivery (~45 min read)** — a confidential mid-tier scope document, before any contract 5. **Paid live working session (~2-3 hours, $300 paid for your time)** — Zoom with screen-share, architectural discussion + bounded live coding task, with a senior technical reviewer present. This is the verification step that matters most. You're paid for the session regardless of whether we proceed. 6. **NDA + full briefing** — released only after the live session passes 7. **Contract** — milestone-based Upwork escrow If you're not comfortable with the paid observed verification step, this isn't the right project for you. We've found it's the only reliable way to verify what we need to verify, and senior developers confident in their work generally welcome it. What We're Looking For: Strong candidates have: - Built a Stripe Connect Express marketplace before (or comparable level of Stripe Connect depth) — destination charges, manual transfers, custom payout schedules - Hands-on experience with Stripe Checkout (hosted) with payment_intent_data for marketplace flows - Built a payment provider abstraction layer in PHP (non-negotiable architectural requirement for this project) - Hands-on AWS SDK for PHP experience with S3 + pre-signed URLs (not just WP Offload Media) - Comfortable with rigorous fixed-price engagements with clear milestones, staging-site-only development, and independent third-party audit at final milestone - Comfortable with paid observed live verification before contract signing This is a long engagement (9-14 weeks calendar time) for a senior developer. We're not looking for the cheapest bid — we're looking for the right developer who can deliver a financially audit-clean plugin. How to Apply: Please answer all five screening questions thoughtfully. Specific lived-experience details (actual error messages, specific webhook events, concrete implementation choices you made for specific reasons) read much stronger than generic well-structured answers. If your application reads strongly, you'll hear back within 5 business days with an acknowledgment and the vertical disclosure. From there, the multi-stage process moves at the pace we can both sustain.