Comparing Property Data API Latency: Realie, RentCast, and ATTOM
Review response times for Realie (9.49 ms), RentCast (439 ms), and ATTOM (441 ms), and see how sub-10 ms vs. ~440 ms latencies impact both bulk data workflows and real-time user experiences.


Josh Dormody
Co-founder & CEO
April 26, 2025
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.
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