Exchanger
A next-generation omnichannel gadget marketplace, device trade-in exchange, repair booking ecosystem, and e-commerce platform.
About The Project
Exchanger is an all-in-one digital gadget commerce and lifecycle ecosystem engineered to simplify how consumers buy, sell, exchange, pre-order, and repair modern consumer electronics in Bangladesh. The platform brings together a high-speed consumer storefront, a dedicated customer classifieds and trade-in exchange portal, a device repair booking service, and an enterprise backoffice suite with integrated POS invoicing and automated bKash payments.
The customer-facing application empowers users to browse brand-new and pre-owned smartphones, laptops, and accessories with granular variant filters (color, storage, condition, regional warranty). Customers can place direct orders, pre-book upcoming flagship releases, initiate instant device trade-in valuations, list peer-to-peer classified ads, book certified hardware repair services, and compare device technical specifications side by side.
The enterprise administration dashboard delivers full operational control to business administrators and technicians, featuring TanStack Table data grids for order fulfillment, automated POS thermal invoice generation (`react-to-print`), dynamic banner and promotional campaign management, multi-level category taxonomy curation, and real-time revenue analytics.
Engineered on a decoupled three-tier architecture, the backend provides high-concurrency Express/TypeScript micro-routes, automated bKash payment gateway callback handling, Redis-backed data caching, hybrid media storage (AWS S3 presigned URLs and Cloudinary WebP optimization pipelines), and strict runtime schema verification powered by Zod.
The Challenge
Consumer electronics marketplaces require intricate data modeling to handle multi-variant hardware combinations (color, storage, region, battery health, condition grading), seamless C2B/C2C trade-in listings, and end-to-end repair tracking while ensuring high performance, instant search latency, zero-friction mobile financial service (bKash) payment verification, and automated invoice dispatch under heavy campaign traffic.
The Solution
Architected a scalable three-tier architecture separating the Next.js 15 consumer client from the Next.js 15 / React 19 administrative suite and Express/TypeScript API core. Developed a 3-level dynamic category specification engine, integrated automated bKash API checkout and instant order verification, implemented dual AWS S3 / Cloudinary media pipelines with Sharp compression, and built an interactive side-by-side spec comparison tool.
Core Features & System Modules
Every feature was purposefully architected for speed, reliability, and ease of operation.
Multi-Variant Gadget E-Commerce
Dynamic product catalog supporting multi-attribute variants (color, storage capacity, regional origin, condition grading) with dynamic pricing and live stock allocation.
C2B & C2C Trade-In Exchange & Ads
Interactive customer exchange portal enabling users to post device ads, submit trade-in valuations, upload condition photos, and connect for device swaps.
Device Repair & Care Booking
Specialized servicing portal where customers choose device models, select specific hardware issues (screen, battery, motherboard), and track repair progress live.
Automated bKash & Cash Payment Gateway
Seamless checkout workflow supporting automated bKash API payment tokenization, instant callback validation (trxID), and cash on delivery.
Side-by-Side Spec Comparison Engine
Interactive device comparison tool (`/compare`) allowing shoppers to compare full technical specifications and benchmark performance between devices.
3-Tier Taxonomy & Dynamic Fields
Hierarchical category architecture (Primary, Secondary, Tertiary) with dynamic custom specification fields tailored for complex electronics attributes.
Printable Invoices & Live Order Tracking
Automated thermal and standard invoice printing engine powered by `react-to-print`, coupled with phone/order-number customer tracking.
Enterprise Admin & Analytics Backoffice
Comprehensive backoffice dashboard with TanStack Table data management, Recharts revenue visualizations, Jodit WYSIWYG blog editor, and banner controls.
Pre-Order & Campaign Deals Engine
Dedicated flagship pre-order workflows with customer deposit management, countdown campaign banners, and promotional discount scheduling.
Architecture & Technical Highlights
Three-Tier Monorepo Separation
Architected three distinct application layers: `exchanger-client` (Next.js 15 consumer storefront), `exchanger-dashboard` (Next.js 15 / React 19 management backoffice), and `exchanger-server` (Express/TypeScript REST API) for isolated scaling and fault tolerance.
Automated bKash Payment Pipeline
Implemented direct bKash merchant integration with dynamic payment URL redirection, backend transaction verification, and instant order transition from pending to paid with real-time customer feedback.
Hybrid Cloud Storage & WebP Media Engine
Engineered dual media handling utilizing AWS S3 presigned URLs for enterprise storage and Multer/Sharp/Cloudinary pipelines for on-the-fly image compression and modern WebP conversions.
3-Level Category & Dynamic Filter Hierarchy
Constructed a relational MongoDB schema modeling Primary, Secondary, and Tertiary categories alongside flexible `ProductField` schemas to dynamically render filterable specification tables across hundreds of gadget variations.
Technologies & Frameworks Deployed
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