HDiDA is an iOS car marketplace that connects private sellers and dealerships with buyers in their area. It is live on the App Store, built universal for iPhone and iPad, and monetized through subscription tiers and a listing boost package rather than commission on sales.

The product is two sided inside a single app. Buyers browse and filter inventory by the attributes that actually matter when car shopping, meaning make, model, year, price, mileage, condition, and proximity, then open a listing with a full photo gallery and vehicle detail. Sellers move through a guided listing flow that handles multi photo upload, description, and pricing. Both sides meet in an in app messaging thread where they can ask questions, arrange a test drive, and negotiate without ever exchanging phone numbers.

The interesting engineering was in the parts users never notice. Photo heavy listings get created on phone networks, so that flow needed client side image compression, resilient uploads, and optimistic UI so a seller with six photos and two bars of signal does not lose a draft. Search had to stay fast against growing inventory with location filtering layered on top of attribute filtering. Messaging needed real time delivery, push notification fallback, and read state that stays consistent when a user switches devices.

Monetization runs through StoreKit with weekly, monthly, and annual tiers plus a boost package that promotes a listing in search results. That meant receipt validation, entitlement state that survives reinstall and device change, and ranking logic that gives boosted listings visibility without making organic results feel worthless. Trust and safety was a hard requirement rather than a nice to have, so the app includes identity verification at signup to cut fraud and spam, encrypted handling of personal and contact data, and privacy disclosures that cleared App Store review at an 18 plus rating.