ListNBuy — Multi-Platform Classifieds Marketplace
A multi-platform buy-and-sell classifieds marketplace featuring real-time buyer-seller chat, interactive location routing with Google Maps, and automated offer negotiation backed by Flutter, Laravel, and WebSockets.
Project Overview
ListNBuy is a multi-platform buy-and-sell classifieds marketplace mobile application engineered in Flutter, connected to a robust Laravel backend with REST APIs and WebSockets.
The application enables users to discover, buy, and sell goods locally with real-time buyer-seller chat, interactive location routing via Google Maps, and automated offer negotiation. Supported by a responsive web portal and a central admin panel managing free vs. premium featured listings, subscription packages, and post-purchase user ratings and reviews.
My Engineering Role
Lead Flutter Mobile Engineer responsible for cross-platform app development, real-time WebSocket messaging, Google Maps Platform route navigation, and Google Play Store publishing.
The Challenge
Building a high-concurrency marketplace with seamless buyer-seller communication, location-based item discovery, and instant push alerts without high server latency.
The Solution
Engineered a responsive Flutter mobile client integrating WebSockets for instant chat and offer notifications, Google Maps SDK for localized radius search, and optimized media compression for rapid photo uploads.
High-Level Architecture
- Flutter mobile application compiled for Android and iOS with clean modular component architecture.
- Real-time WebSocket event connection delivering instant buyer-seller chat messages and typing indicators.
- Google Maps Platform integration with proximity-based radius filtering and turn-by-turn routing to item pickup spots.
- Laravel REST API backend handling product catalogs, user verification, and automated offer negotiation state machines.
- Multi-image compression pipeline optimizing camera uploads before transmitting to storage buckets.
Key Features & Workflows
- Classifieds Discovery & Search: Category filtering across electronics, vehicles, fashion, and home goods with price and distance sliders.
- Real-Time Chat & Offers: In-app WebSocket messaging with formal Make an Offer flows, counter-offers, and acceptance triggers.
- Interactive Map Navigation: View seller item locations on Google Maps and calculate driving routes to agreed pickup zones.
- Featured Listing Subscriptions: Monetization engine supporting premium sponsored ad placement and profile badges.
- User Verification & Ratings: Post-transaction buyer and seller reviews with star ratings and fraud-reporting mechanisms.
- Central Administration Portal: Back-office management of reported listings, category taxonomy, and user bans.
Technical Challenges Overcome
- Managing concurrent negotiation states so buyers and sellers stay synchronized when offers are counter-offered or expired.
- Optimizing client-side map clustering when thousands of active classified items are rendered within dense metropolitan areas.
- Ensuring fast image uploads on cellular networks through progressive client-side JPEG compression.
Production Results & Impact
- Successfully launched on Google Play Store (com.alrighttech.listnbuyapp).
- Public video demonstration accessible showcasing listing creation, map exploration, and live chat.
- Delivered a dependable mobile marketplace connecting local buyers and sellers seamlessly.
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