At SmartyStreets we're proud of our speed, but how fast is fast? No one wants to spend more time than necessary dealing with bad addresses, and shaving seconds off your site's checkout process can have big benefits. Our SLA guarantees sub-100ms response times for address lookups, not including external network latency. When you factor in external latency, the address lookup response will often come back in around 160ms (although this varies widely depending on many factors).
You can always check out response times on our status page, and you can ping our servers to get a real-time idea of the actual delay.
To get the most out of our address API, you can optimize performance with a few tricks, including HTTP keep-alive and asynchronous I/O. Check out our Best Practices page for more tips and how-to's.