Case Study

Web

MegaMart – Multi-Vendor E-Commerce Platform

MegaMart is an enterprise-grade multi-vendor e-commerce platform built with Next.js 16 and React 19. The application operates as a three-sided ecosystem: a high-conversion consumer storefront for shoppers, a specialized Seller Central hub for merchant operations (catalog, inventory, orders, logistics, and payouts), and a Master Admin portal for platform governance, merchant KYC verification, and financial settlements. The system is backed by cookie-based JWT authentication with proactive silent token refreshing, role-based route shielding, and reactive data visualization.

Next.js

Tailwind CSS

REST API

MegaMart – Multi-Vendor E-Commerce Platform screen 1

MegaMart – Multi-Vendor E-Commerce Platform screen 2

MegaMart – Multi-Vendor E-Commerce Platform screen 3

MegaMart – Multi-Vendor E-Commerce Platform screen 10

MegaMart – Multi-Vendor E-Commerce Platform screen 11

Challenges & solutions

The technical problems our team solved to ship a reliable, unified web experience.

Managing three distinct user roles (Customer, Seller, Admin) under a single domain without routing conflicts or allowing unauthorized cross-portal access (e.g., sellers accessing customer accounts or customers accessing seller hubs).

Implemented a Next.js proxy middleware layer (`src/proxy.ts`) combined with client/server JWT payload decoding (`parseRole`). It intercepts requests on protected path matchers (`/seller/*`, `/account/*`, `/admin/*`), checks role permissions from auth cookies, and executes instantaneous redirects before sensitive page components are rendered.

Token expiration during complex multi-step seller product creation or customer checkout workflows caused sudden session loss, dropped form states, and authorization errors.

Built a custom API client (`apiClient`) featuring an automatic 401 retry queue with proactive JWT expiration checks (`decodeJwtPayload`). When a token nears expiry or expires mid-session, outbound requests are temporarily held while a silent token refresh call updates cookies and localStorage, after which queued requests replay automatically without user interruption.

Maintaining real-time reactivity between global shopping cart badges, wishlist toggle buttons, and customer session across deep component trees without redundant re-renders or stale localStorage state.

Architected decoupled React Context providers (`CartContext`, `WishlistContext`, `AuthContext`) with optimistic UI updates and background API synchronization, delivering instantaneous UI feedback while guaranteeing server-side data integrity.

Authoring products with complex variant matrices (size, color, price, stock) and filtering queries often resulted in empty string values or enum validation rejections from the backend.

Designed a modular `product-form.tsx` backed by strict TypeScript schema definitions, combined with query sanitization utilities (`cleanQuery`) that automatically strip empty strings, `undefined`, and "all" values before API dispatch.

Key features

What users get in the finished, shipped product.

Tri-Role Authentication & Route Shielding (Proxy Middleware)

Overview: Unified authentication gateway handling shoppers, sellers, and platform administrators with complete session isolation.
Features: Cookie-backed JWT authentication, Next.js proxy middleware route guards (`/account/*`, `/seller/*`, `/admin/*`), safe role payload decoding (`parseRole`), and automated redirection ensuring sellers are restricted to Seller Central and shoppers cannot enter merchant panels.

Dynamic Storefront & Interactive Discovery

Overview: Consumer-facing shopping hub designed for fast discovery and engagement through interactive UI elements.
Features: Responsive hero banners, flash deal section with real-time countdown timers, interactive clothing rail showcase powered by GSAP animations, dynamic category navigation sidebar, and curated top brands.

Multi-Faceted Product Exploration & Filtering

Overview: Flexible search and filtering engine allowing shoppers to quickly narrow down vast catalogs.
Features: Real-time keyword search, multi-attribute filtering (categories, price sliders, star ratings, brand selection), sorting algorithms (Price Low/High, Newest, Popularity), and responsive grid-to-list layout toggles.

Product Details, Rich Media Gallery & Buy-Box Experience

Overview: Comprehensive product presentation layer designed to drive conversion with rich visual media and live availability checks.
Features: High-resolution multi-image zoom gallery with thumbnail navigation, variant pickers (size, color, SKU), real-time stock availability badges, customer review and rating breakdowns, delivery pincode availability checks, and a sticky Buy-Box (`Add to Cart`, `Buy Now`).

Reactive Shopping Cart, Wishlist & Checkout Workflow

Overview: Context-driven shopping state synchronization with guest-to-authenticated state preservation.
Features: Slide-over cart drawer and dedicated cart page, instant item quantity adjustments, one-click wishlist toggling, coupon validation engine with instant discount recalculation, multi-address management, and itemized billing summaries.

Seller Central – Catalog, Variant & Inventory Lifecycle

Overview: Dedicated merchant workspace for authoring product listings, configuring SKUs, and auditing stock levels.
Features: Comprehensive multi-attribute product authoring form (`/seller/products/new`, `[id]/edit`), multi-image uploads, dynamic variant matrices, real-time stock inventory adjustments (`/seller/inventory`), and low-stock warning indicators.

Seller Order Fulfillment, Logistics & Returns Processing

Overview: End-to-end merchant fulfillment pipeline covering order dispatch, carrier tracking, and return resolutions.
Features: Real-time order queue with status filtering (Pending, Processing, Shipped, Delivered, Cancelled), order detail drill-downs (`/seller/orders/[id]`), shipment label creation with tracking codes, return request inspection (`/seller/returns`), and refund approvals.

Seller Financial Hub & Payout Management

Overview: Merchant accounting workspace for tracking platform commissions, net settlement balances, and bank payouts.
Features: Financial dashboard (`/seller/payments`) displaying Available Balance, Pending Settlements, and Lifetime Sales, bank account setup, payout request history, and transaction ledger breakdowns.

Master Admin Governance, KYC Verification & Settlement Approvals

Overview: Platform governance control center granting administrators complete oversight over marketplace participants and finances.
Features: Executive dashboard tracking GMV, revenue charts (`Recharts`), top categories distribution, merchant review dialog (`SellerReviewDialog`) for KYC approval/rejection, customer suspension tools, and multi-state payout disbursement approvals (`PayoutActionDialog`).

Tech integrations

Third-party SDKs & libraries

7 core integrations powered

Shadcn UI

Core system integration

Base UI

Core system integration

Recharts

Core system integration

GSAP

Core system integration

Lucide React

Core system integration

Next.js Proxy/Middleware

Core system integration

JWT Cookie & Local Storage Session Synchronization.

Core system integration

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