Proptech/Engineer

Built the buy-side. Then taught it to understand what buyers actually mean.

The nation's largest flat fee brokerage had a sell-side business but no way for buyers to search, discover, or transact. We built the marketplace and a proof-of-concept for AI-powered property search that understands context, not just filters.

Client
National Proptech Platform
Engagement
Multi-phase engagement
Focus
Marketplace Build + AI Search
Compliance
MLS data compliance
Buy-side marketplace and agentic property search for a national brokerage

01

The work

The nation's largest flat fee MLS brokerage, licensed in all 50 states, operating one of the top 10 most visited proptech sites in the country. Hundreds of homes sold annually through a technology-driven model that cuts traditional agent commissions.

What was getting in the way

  • No buy-side product at all. Buyers had no way to search, discover, or transact through the platform.
  • The entire buy-side of the market was going to Zillow, Compass, and Redfin.
  • No integrated path from property discovery to closing. Title and mortgage were separate, disconnected steps.
  • Property search across the industry was limited to structured filters. No platform understood contextual intent.
  • The company was capturing value on listings but losing it completely on the buying side.

02

What changed

Build the marketplace. Then make search smarter than anyone else's.

We built a complete buy-side web application from scratch. Mobile-responsive, consumer-grade, handling MLS data from all 50 states. Buyers can search, filter, favorite, and discover properties the way they expect from a Zillow or Compass — but integrated with the client's flat fee model.

03

What we built

Then we wired in the transaction layer. Title and mortgage services integrated directly into the buying experience so a buyer can go from discovering a property to closing on it without leaving the platform. That's full transaction capture — listing through closing — in one product.

On top of that, we built a proof of concept for AI-powered property search. Instead of structured filters, buyers type what they mean: "townhome in Lexington, Kentucky near Whole Foods." The engine parses the intent — property type, location, proximity to a specific amenity — and returns results that match. It's among the first implementations of semantic property search in the US market.

Product EngineeringAI AgentsNLP / Semantic SearchSystem Integration

04

How it works

  • Buy-side marketplace launched and running across all 50 states. The client operates it today.
  • Title and mortgage workflows integrated into the transaction flow. Discovery to closing in one platform.
  • MLS data feeds connected from all 50 states into a consumer-grade search experience
  • NLP-powered property search POC built and validated — contextual queries, amenity proximity, natural language understanding
  • Full transaction capture: the #1 flat fee brokerage now has both sell-side and buy-side surfaces
  • Among the first semantic property search implementations in US proptech

05

Business impact

states
50
states
Buy-side marketplace live across all 50 states
proptech site
Top 10
proptech site
Platform ranks among the most visited proptech sites in the US
semantic search
First
semantic search
Among the first NLP-powered property search implementations in US proptech
“AppStream didn't just build us a buy-side app. They gave us a search experience that none of our competitors have.”
Product Lead, National Flat Fee Brokerage

06

What’s next

Build the product your competitors don't have yet

If you're sitting on a market opportunity that needs a new product surface and AI differentiation, we've done this before.

Talk to an AI engineerMore work

Team

  • Justin TannenbaumSolutions Architect
  • Lukasz ChmielewskiLead Engineer
  • Piotrek SzyperskiEngineering
  • Ernesto QuispeProduct Design

Stack

.NET · C# · React · TypeScript · Azure · SQL · NLP · MAF

More work

Keep reading.