Senior WooCommerce Engineer Needed — Audit, Stabilize & Complete Custom Plugin (LME + WWEX API)

I have a WooCommerce site with a custom aluminum pricing system built around: LME-based price calculations custom weight/height formulas custom order builder custom plugin logic Worldwide Express (WWEX) shipping API integration The core logic exists, but the system is not stable enough to launch. Shipping rates are incorrect, API responses are inconsistent, and staging is fragile. I need a senior-level WordPress/WooCommerce engineer to: audit the entire system stabilize the custom plugin fix shipping + API logic complete missing integrations test end-to-end deliver a launch-ready staging environment This is NOT a basic WooCommerce customization job — only senior-level engineers should apply. You must be comfortable with custom PHP, API integrations, complex formulas, and debugging fragile systems. ⭐ Deliverables (Explicit List) The freelancer must deliver: A complete audit report (Milestone 1) A fully stabilized custom plugin Corrected weight/height logic Corrected shipping rate logic Corrected WWEX API integration A fully functional checkout flow A stable staging environment A full testing report (Milestone 3) A launch-ready migration plan A rollback plan ⭐ Milestones & Deliverables Milestone 1 — Audit (48–72 hours) Deliverable: A written audit report detailing: *what works *what is broken *what is missing *what must be rebuilt *estimated hours for each fix Audit includes: Custom plugin code LME logic + formulas Weight/height integration Custom order builder WWEX API integration Shipping rate logic Checkout flow Staging stability Milestone 2 — Fix & Stabilize (5–10 days) Deliverable: A fully functional, stable staging environment. Work includes: Fix weight/height integration Fix shipping rate logic Fix WWEX API calls Fix checkout issues Fix staging errors Finalize custom order builder Stabilize plugin code Milestone 3 — End-to-End Testing (2–4 days) Deliverable: A testing report confirming launch readiness. Testing includes: Custom order → LME bot output Weight/height → shipping rate WWEX API response Checkout flow Edge cases Milestone 4 — Launch Preparation (1–2 days) Deliverables: Launch-ready staging Migration plan Rollback plan ⭐ Timeline (Full Project) Milestone 1 — Audit: 48–72 hours Milestone 2 — Fix & Stabilize: 5–10 days Milestone 3 — Testing: 2–4 days Milestone 4 — Launch Prep: 1–2 days Total estimated timeline: 10–18 days depending on audit findings. ⭐ Budget Structure (Fixed Price Only) Milestone 1 (Audit): $150–$300 Milestone 2 (Fix & Stabilize): $1,500–$4,000 (based on audit) Milestone 3 (Testing): $300–$600 Milestone 4 (Launch Prep): $200–$400 This project is fixed-price only. No hourly billing. No open-ended work. ⭐ Required Skills Advanced PHP Advanced WooCommerce customization Custom plugin development API integrations (REST/XML) Shipping API experience (UPS/USPS/FedEx/WWEX preferred) Debugging fragile systems Staging → production migration Complex formula implementation High-level problem solving ⭐ Disqualifiers (Do NOT apply if…) You rely on page builders only You only do theme customization You cannot read or write custom PHP You cannot debug API integrations You cannot work with complex formulas You cannot deliver fixed-price milestones You cannot provide daily updates You cannot work on staging environments You cannot audit someone else’s code ⭐ Application Requirements (Mandatory) To apply, you must provide: A short explanation of your experience with custom WooCommerce plugins A short explanation of your experience with shipping APIs A short explanation of your experience stabilizing fragile systems A link to 1–3 relevant projects Your proposed fixed price for Milestone 1 (Audit) Your estimated timeline for Milestone 1 Applications missing any of these items will be ignored. ⭐ Technical Test (Mandatory) Please answer this in your proposal: “Explain how you would debug a WooCommerce shipping rate that returns incorrect values from a third-party API.” ⭐ Additional Requirements (Important) Daily progress updates required All work must be done directly on staging (no local-only development) Milestone 2 pricing must include a line-item breakdown based on the audit These requirements ensure transparency, accountability, and predictable progress. ⭐ Final Notes This project is already far along — the core logic exists — but it needs a senior engineer to stabilize and finish it. If you are confident in: custom PHP WooCommerce internals API debugging plugin architecture complex formulas shipping logic Then you will be able to complete this project successfully.