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

Intro

In today’s data-driven environment, real estate applications depend on low API latency to differentiate between a smooth user experience and a sluggish interface. This post compares average response times for three popular property data APIs—Realie, RealEstateAPI (REAPI), 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: 9.49 ms

• RealEstateAPI (REAPI): 122 ms (P95)

• RentCast: 439 ms

• ATTOM: 441 ms

Figure 1: 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 16, 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.\

RealEstateAPI Metrics

• P95 latency (7-day avg): 122 ms (P50 Latency not displayed)

Figure 4: RealEstateAPI P95 latency of 122 ms. (P50 Latency not displayed)

Realie API Metrics

• Average latency: 9.49 ms

  

Figure 5: Realie’s log showing average latency sub-10 ms.

What the Numbers Mean

For High-Volume Data Workloads

• Throughput:

  • Fetching 100 records sequentially takes under 1 s with Realie,

  • ~12 s with REAPI

  • ~44 s with RentCast or ATTOM.

• Infrastructure simplicity:

  • At ~10 ms per call, single-threaded, request-response code suffices;

  • Around ~400 ms, you often need parallelism, batching, or caching to maintain performance

For Interactive, Customer-Facing Apps

User perception:

• Interactions under 0.1 s feel instantaneous;

• Delays above 1 s break a user’s flow.

• Realie’s ~0.01 s sits well below the “instant” threshold;

• REAPI’s ~0.122 s and RentCast/ATTOM’s ~0.44 s approach the point where users will notice delays—especially as calls stack.

Performance budget:

• A 10 ms data fetch preserves headroom for additional processing;

• A 122–441 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.

• RealEstateAPI (REAPI) operates at ~122 ms, which may suffice for many batch-oriented tasks but can introduce perceptible delays in real-time scenarios.

• RentCast and ATTOM both hover around ~440 ms on average, suitable for bulk jobs but slower for interactive use.

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 response times can vary by over 40× between providers. Choose the API whose performance profile best matches your application’s needs.