The minimal testing done four days before the launch of HealthCare.gov failed to handle 500 people applying through the website at one time, according to internal e-mails between the top Obama administration technicians working on the site.

“I DO NOT WANT A REPEAT OF WHAT HAPPENED NEAR THE END OF DECEMBER 2005 WHERE MEDICARE.GOV HAD A MELTDOWN (THIS IS TO GET YOUR ATTENTION IF I DIDN’T HAVE IT ALREADY,” Deputy Chief Information Officer Henry Chao of the Center for Medicare and Medicaid Services wrote to dozens of people working on the site after he reviewed some of the testing Sept. 26. …

“I realize everything is a priority but…the facts are that we have not successfully [handled] more than 500 concurrent users filling out applications in an environment that is similarly in size to Day 1 production,” Acting Director of the CMS Office of Enterprise Management David Nelson wrote in an e-mail on Sept. 27. “We cannot proactively find or replicate actual production capacity problems without an appropriately sized operational performance testing environment.”