Karnival — City-Based Geospatial Classifieds & Marketplace
Hyper-local classified ad platform powered by PostGIS spatial queries, interactive map clustering, and real-time buyer-seller chat.
Karnival (`com.karnival.android`) is a city-centric classifieds and peer-to-peer marketplace application engineered by NEURALXCIPHER (PRIVATE) LIMITED. Built with Flutter, REST APIs, and PostGIS spatial indexing, it enables users to post listings in under 60 seconds, explore nearby deals via clustered interactive maps, and negotiate directly through real-time in-app messaging.
Full classifieds marketplace shipped (`com.karnival.android`)
Radius & neighborhood-level geospatial discovery
Smooth map panning across dense urban listing zones
Domain Background
Peer-to-peer classified platforms succeed or fail on two metrics: how effortlessly a seller can post an item, and how accurately a buyer can filter items within their immediate neighborhood.
Why Standard Approaches Failed
Naive latitude/longitude bounding queries slow down exponentially as listing volume grows, and rendering ratusan map pins simultaneously freezes mobile map views.
Non-Negotiable System Targets
- Execute radius and city-level multi-attribute filtering (price, condition, category, distance) with low latency.
- Cluster dense map markers dynamically as the user pans and zooms.
- Provide instant in-app chat between buyers and sellers without exposing personal phone numbers prematurely.
How neuralXcipher Engineered the Solution
We paired a responsive Flutter client with a spatial backend utilizing PostGIS geography indexes (`ST_DWithin`) and viewport-based marker clustering, alongside a multi-step camera/gallery listing composer with client-side image compression.
Layered Engineering Specification
Geospatial search and real-time messaging architecture for high-density local listings.
Switches fluidly between infinite-scroll card feeds and interactive clustered map exploration.
Executes combined full-text, category attribute, and geospatial radius queries.
Optimizes multi-photo listing uploads and powers listing-contextualized chat threads.
Core Capabilities Shipped
PostGIS Geospatial Radius Search
Pinpoints listings within exact kilometer radii or city boundaries.
Viewport Map Pin Clustering
Groups dense neighborhood listings into smooth interactive clusters at 60fps.
Contextual Buyer-Seller Chat
Direct negotiation threads linked to specific ad listings with push alerts.
How We Solved Edge-Case Bottlenecks
Slow photo uploads when sellers attach 5–10 high-resolution smartphone camera images.
Implemented background isolate image resizing and WebP/JPEG compression prior to multipart upload.
- Privacy-first messaging that masks personal contact info until seller approval.
- Indexed spatial queries maintaining fast response times across large listing tables.
- Production Flutter mobile app (`com.karnival.android`)
- Spatial search & classified listing backend API
- In-app chat and push notification integration
Production Interface Gallery
Hardware-accelerated 60–120fps iOS, Android, Wear OS, and Web applications engineered from a single, strictly-typed Dart codebase.
High-concurrency Node.js, NestJS, PostgreSQL, and Supabase backends engineered for sub-100ms p95 latency and strict security.
End-to-end multi-role platforms uniting buyers, sellers, couriers, and administrators across mobile and web.
Unified super-app marketplace connecting local merchants, service freelancers, and consumers across Spain and Latin America.
Sub-second WebSocket bidding marketplace, dual buyer/seller profile switching, and automated invoice generation for the Australian market.
High-conversion Flutter retail shopping app engineered with Firebase Cloud Firestore real-time catalog streaming and offline cart survival.
Building a Local Classifieds, Real Estate, or Directory Platform?
We engineer high-speed PostGIS spatial search and map-driven mobile apps.