Quick Answer
Choose an API by measuring the endpoints you need from your application’s region. Realie’s API has ~20 ms average latency. In a separate September 2026 ATTOM benchmark, ATTOM Basic Profile averaged 232.6 ms (minimum 108.5 ms, P90 325.0 ms) on a fixed 100-property set — a different measurement from Realie’s published average. Verify competitor latency on each vendor’s own site and from your stack before comparing providers.
Summary
The right latency target depends on the application. Test complete round trips, error rates, and tail latency with representative identifiers and concurrency. Use those results alongside coverage, freshness, pricing, and rate limits when deciding whether to fetch during a live request, cache a result, or process it in a background job.
The infrastructure you avoid
When an API is slow, teams compensate: a queue to move the call off the request path, a cache to avoid repeating it, a scheduled job to warm that cache, and monitoring for all three. Each piece is reasonable on its own, and together they are a meaningful share of a small team’s engineering time.
Faster responses can reduce waiting, but they do not remove the need to plan for rate limits, outages, or freshness. Decide which results to cache from measured behavior and your product’s requirements.
Measuring it honestly
Test from where your servers run, not from a laptop on a home connection. Use identifiers drawn from your actual workload. Measure the complete round trip including TLS and JSON parsing, since that is what your users experience.
Then look at the tail. A 9 ms median with a 2-second p99 will still time out under load. Percentiles tell you what your worst requests look like, and those are the ones that generate support tickets.
Sources
Frequently asked questions
- How should I compare latency numbers across vendors?
- Use the same endpoint, geography, concurrency, and percentile definitions in your own test. Means, medians, and P95 figures from different dashboards are not directly comparable. Verify each vendor’s current figures on that vendor’s documentation.
- Does latency change with plan tier?
- Published tiers share endpoint and data-type access, with different allowances and overage rates. Measure response times for your workload rather than assuming identical latency.
- What is the rate limit?
- Check the current endpoint documentation for rate limits. Supported search endpoints return pages of up to 100 parcels; address and parcel ID lookups return one record.
- Can I use this in a user-facing search box?
- You can use property lookups in a search interface. Measure the full request path and rate limits first, then choose caching and loading behavior that fits your response-time budget.