How MLS Data Sync Actually Works (And Why So Few Companies Get It Right)

How MLS Data Sync Actually Works (And Why So Few Companies Get It Right)

When you search for homes on a real estate website, the results feel simple — type a city, set a price range, see listings. Behind the scenes, making that work is one of the most complex technical challenges in real estate technology. Fewer than 10 companies worldwide have built it from the ground up.

What Is MLS Data Sync?

Multiple Listing Services (MLS) are the databases where agents and brokers share listing information. There are over 500 MLS boards in the United States alone, each running different software, different data formats, and different rules about how that data can be displayed.

MLS data sync means connecting to these databases, ingesting listing data in real time, normalizing it into a consistent format, and displaying it on websites with search, filtering, and mapping capabilities — all while staying compliant with each board's display rules.

Why It's So Hard

No universal standard. While RESO (Real Estate Standards Organization) has pushed for data standardization, the reality is that each MLS still has quirks. Field names differ, photo delivery methods vary, and some boards update every 15 minutes while others batch updates once daily.

Volume is massive. A single MLS board might have 50,000 active listings, each with 20+ photos and hundreds of data fields. When you're syncing 110+ boards, you're processing millions of listings and tens of millions of images — continuously.

Compliance is strict. Every MLS has specific rules about how data can be displayed, what disclaimers must appear, and how quickly removed listings must be taken down. A single compliance violation can get your data access revoked.

Speed matters. Buyers expect real-time results. If a listing goes pending at 2 PM, your site needs to reflect that within minutes, not hours. Stale data erodes trust and frustrates users.

How CloseHack Does It

Our MLS sync infrastructure is built on AWS and designed to handle the scale and complexity of 110+ MLS board connections. The system runs continuous polling cycles that detect changes — new listings, price updates, status changes, photo additions — and propagates them across all connected websites within minutes.

Data normalization happens at the ingestion layer. Regardless of whether an MLS calls it "list price" or "asking price" or "current price," our system maps it to a consistent schema that our search engine can query instantly.

Photo processing is a pipeline unto itself. Images are downloaded, optimized for web delivery in multiple resolutions, cached on our CDN, and linked to their listings — all automatically. When an agent uploads new photos to their MLS, they appear on their CloseHack site without lifting a finger.

Why This Matters for Agents

You don't need to understand the engineering to benefit from it. What matters is that when a buyer searches your site, they see every listing in your market, updated in real time. When a listing goes pending, it's reflected immediately. When new photos are added, they show up automatically. And when you pull a market report, the data is current.

The alternative — manually uploading listings, dealing with stale data, or relying on a vendor with spotty MLS coverage — is how leads get lost and trust gets broken.

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CloseHack's MLS sync technology connects to 110+ boards nationwide with real-time data updates, automated photo processing, and full RESO compliance.