Full-Stack Shopify Developer

Full-Stack Shopify Developer — Omni-Channel Cake Ordering Platform We are a product development agency building a production-grade, Shopify-centred omni-channel ordering platform for a fast-growing bakery brand in Uganda. The platform unifies a Shopify website storefront and a Meta WhatsApp Business ordering flow into a single commerce engine — complete with Uganda-compatible payment gateways (MTN Mobile Money, Airtel Money, Pesapal, Flutterwave), inFlow inventory/manufacturing integration, QuickBooks finance sync, automated customer notifications, delivery zone management, and a full analytics layer. This is not a template-install or theme-customisation engagement. We are looking for a senior engineer who can architect, build, and own a complex, multi-system integration from the ground up. If you've shipped real Shopify custom apps, wired WhatsApp Business API end-to-end, and worked with African payment ecosystems — this is built for you. What You'll Build The engagement covers 15 feature modules across four delivery phases: Phase 1 — Foundation & Core Commerce ▸ Shopify custom theme (Liquid) — mobile-first, brand-consistent, performance-optimised ▸ Full product catalogue: multi-size variants, SKUs, flavour/colour/add-on options, allergen info ▸ Availability engine: statuses (available / limited / out-of-stock / fully booked), date-specific availability, production-capacity validation ▸ Website ordering: live price calculator, cart, guest + account checkout, delivery/collection, time-slot booking, order tracking Phase 2 — Payments, Inventory & Production ▸ Pesapal integration: MTN Mobile Money, Airtel Money, Visa/Mastercard, bank transfer ▸ Flutterwave as secondary/international gateway — multi-currency, modern checkout ▸ Payment webhook processing, failed/pending/expired flows, full & partial refunds, reconciliation ▸ Duplicate payment protection and idempotent order processing ▸ inFlow Inventory/Manufacturing API: BOMs, size-specific ingredient quantities, manufacturing-order creation on payment, production stages, staff assignments, reorder alerts, daily capacity limits Phase 3 — WhatsApp Flow & Customer Communications ▸ Meta WhatsApp Business API + Flow Builder: dynamic catalogue, guided ordering, delivery details ▸ Custom Node.js WhatsApp Flow endpoint — Shopify cart/draft order creation from WhatsApp sessions ▸ Sales-channel tagging, duplicate-order protection, webhook error logging and retry logic ▸ Full automated WhatsApp notification suite: order confirm → payment → production → ready/dispatch → delivery → refund → feedback ▸ Shared customer-support inbox handover Phase 4 — Delivery, Finance, Analytics & Launch ▸ Delivery zone configuration, address/landmark/map-pin collection, logistics-provider API integration ▸ Rider assignment, delivery status, ETA, proof of delivery, failed-delivery handling ▸ QuickBooks Online sync: sales, gateway fees, refunds, delivery income/costs, ingredient costs, product profitability ▸ Analytics: conversion rates, abandonment, cake demand, payment success, production delays, on-time delivery, channel profitability ▸ full handover