As the Obama administration’s weekend deadline for a smoothly functioning online marketplace for health insurance arrives, more than a month of frantic repair work is paying off with fewer crashes and error messages and speedier loading of pages, according to government officials, groups that help people enroll and experts involved in the project.

But specialists said weeks of work lie ahead if the $630 million site, Healthcare.gov, is to accommodate the expected flood of people seeking to buy health insurance, including a major reconfiguration of much of the computer hardware. Without the additional changes, experts predict, the website may continue to crash during periods of peak usage.

Beyond the prospect of potential delays for consumers, insurers warn that problems remain in the invisible “back end” that transmits enrollment information to them. That data has been plagued by inaccuracies, insurers say. Administration officials have been unwilling to disclose the error rate.

As late as Wednesday, the site still continued to slow down when 30,000 users tried to log on simultaneously, according to project specialists. A batch of hardware upgrades and software fixes scheduled for this weekend, administration officials say, will allow the site to handle 50,000 simultaneous users, as promised, by Sunday.

Although the administration has postponed a December marketing campaign, fearful that the site would collapse under a surge in traffic, five weeks of repair work have clearly made the exchange better. From last Sunday to Tuesday, nearly 20,000 users managed to enroll in insurance plans, the most for a three-day period, according to people familiar with the project. By comparison, fewer than 27,000 users picked an insurance plan on the federal site in the entire month of October.

But the pace of enrollment must pick up drastically if the administration is to meet its target of signing up 7 million people by the end of March, the number that insurers say they need to spread risks and keep prices down. While some states that built their own sites are making better progress enrolling people, applicants in 36 states, with two-thirds of the nation’s population, depend on the federal site.

At this week’s rate of enrollment, those enrolled through the federal exchange would total fewer than 1.1 million by the March deadline. Few insurance executives expect alternative options for enrolling, including by phone, mail or in person at counseling centers, to make up that gap.

The administration has already spent more than $9 million beefing up the system’s computing power with additional servers and other hardware. The reconfiguration of the data center — the website’s computer brain — is expected to cost millions more and require up to another month of work, specialists said.

Experts involved in the repair work say the overhaul is necessary because bursts of traffic beyond the designed capacity could bog down the site, forcing users into an electronic queue until emails notify them that they can return.

The only solution, several experts said, is to reconfigure many of the site’s computer servers so that they are dedicated solely to HealthCare.gov’s tasks. Currently, most of the servers juggle demands from other clients as well.

One expert said the site needs to be able to handle 100,000 simultaneous users to provide a safe margin of error.

“Think of it as Version Two,” he said.

Tests conducted this week for The New York Times by a California-based company that evaluates websites for major commercial clients found that the site remains too complicated for many users and is still prone to errors and delays.

Federal officials continue to try to create alternative ways to enroll. The latest is a shortcut called EZ-App, which will allow consumers to more easily estimate how much federal assistance they are eligible to receive.

The concept is similar to the Internal Revenue Service’s 1040EZ form, the shortest and simplest way to file a federal income tax return. But even getting this slimmed-down process to work online has proved difficult, one person said, so it will initially only be available to individuals who seek to enroll by telephone.