Comparing Property Data API Latency: Realie, RentCast, and ATTOM

Intro

In today’s data-driven real estate applications, API latency can make the difference between a smooth user experience and a sluggish interface. This post compares average response times for three popular property data APIs—Realie, RentCast, and ATTOM—and explains what those differences mean in practice.

Latency Benchmark Overview

We ran a consistent latency test across all three APIs under similar network conditions. The average response times were:

• Realie: 9.8 ms

• RentCast: 439 ms

• ATTOM: 441 ms

Below is a bar chart illustrating the gap between sub-10 ms responses and those that approach half a second:

Live Dashboard Metrics

To verify these benchmarked figures, we pulled each provider’s own reported metrics directly from their dashboards on April 24, 2025.

RentCast API Metrics

• Average latency: 439 ms

• Maximum observed latency: 7184 ms

Figure 2: RentCast’s dashboard confirms an average response time of just under half a second, with spikes up to ~7 s.

ATTOM API Status

• Average response time (7-day avg): 441 ms

• Uptime (7-day avg): 99.5 %

Figure 3: ATTOM’s status page shows consistent sub-500 ms averages alongside high availability.

What the Numbers Mean

For High-Volume Data Workloads

• Throughput: Fetching 100 records sequentially takes under 1 s with Realie but around 44 s with RentCast or ATTOM.

• Infrastructure simplicity: Single-threaded, request-response code suffices at ~10 ms; at ~440 ms, parallelism, batching, or caching is often required to maintain acceptable performance.

For Interactive, Customer-Facing Apps

• User perception: Studies indicate interactions under 0.1 s feel instantaneous, while delays above 1 s break a user’s flow. Realie’s ~0.01 s latency sits well below the “instant” threshold; RentCast’s and ATTOM’s ~0.44 s rates approach the point where users will notice delays—especially as calls stack.

• Performance budget: In systems with strict SLAs, a 10 ms data fetch preserves headroom for additional processing; a 440 ms fetch consumes a large portion of the total response-time budget.

Conclusion

• Realie delivers sub-10 ms average latency, enabling ultra-responsive integrations and workflows.

• RentCast and ATTOM both operate around 440 ms on average, which may be sufficient for many batch-oriented tasks but could introduce perceptible delays in real-time scenarios.

Latency is just one factor—data coverage, pricing, feature set, and reliability also play key roles. However, when raw speed is the priority, these benchmarks show how response times can vary by over 40× between providers. Choose the API whose performance profile best matches your application’s needs.