As questions mount over the website's failure, insider interviews and a review of technical specifications by The Associated Press found a mind-numbingly complex system put together by harried programmers who pushed out a final product that congressional investigators said was tested by the government and not private developers with more expertise.

Project developers who spoke to the AP on condition of anonymity — because they feared they would otherwise be fired — said they raised doubts among themselves whether the website could be ready in time. They complained openly to each other about what they considered tight and unrealistic deadlines. One was nearly brought to tears over the stress of finishing on time, one developer said. Website builders saw red flags for months.

A review of internal architectural diagrams obtained by the AP revealed the system's complexity. Insurance applicants have a host of personal information verified, including income and immigration status. The system connects to other federal computer networks, including ones at the Social Security Administration, IRS, Veterans Administration, Office of Personnel Management and the Peace Corps.

Days before the launch of President Obama’s online health ­insurance marketplace, government officials and contractors tested a key part of the Web site to see whether it could handle tens of thousands of consumers at the same time. It crashed after a simulation in which just a few hundred people tried to log on simultaneously.

Despite the failed test, federal health officials plowed ahead.

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The Centers for Medicare and Medicaid Services (CMS), the federal agency in charge of running the health insurance exchange in 36 states, invited about 10 insurers to give advice and help test the Web site.

About a month before the exchange opened, this testing group urged agency officials not to launch it nationwide because it was still riddled with problems, according to an insurance IT executive who was close to the rollout.