Peak census web traffic pegged at 120,000 simultaneous users

The Census Bureau is expecting a maximum of 120,000 concurrent respondents to its internet self-response page during the 2020 population count, but it's preparing for much higher loads.

The bureau's current plan is to make sure the system can handle a contingency of 600,000 concurrent users, Michael Thieme, the bureau's assistant director for decennial census programs, systems and contracts, said at the bureau's May 2 National Advisory Committee meeting.

A single internet self-response computer cluster in the Amazon government cloud can "comfortably handle" about 50,000 users at once, meaning the contingency load can support that of 12 AWS clusters, said Thieme.

"This is the first time we're going to have this as the bulwark of the decennial census," he said. "If for whatever reason, we have a news story or our ad campaign is just performing through the roof and we get a viral response, we think that that maximum right now would be 600,000 at-the-same-second users."

So far, the bureau has been able to handle the load in testing, said Census CIO Kevin Smith. In a field test held as part of end-to-end testing in Providence, R.I., about 60 percent of respondents filled out the census survey online.

In 2016, the Australian census was taken down by a brute force attack that flooded the IT infrastructure. Smith has said the bureau has other plans in place to protect against such an attack, and it hopes to limit a similar possibility in 2020 because of the bureau's information sharing with the Department of Homeland Security and the intelligence community.

The Government Accountability Office recently found the bureau lacks a formal process for tracking and completing recommendations from DHS on its cybersecurity posture. At the meeting, though, Smith said the two agencies have been going back and forth within existing workflows and that the relationship with DHS has been fruitful as the bureau continues its cybersecurity prep.