A surge of signups is expected this week as Obamacare’s open enrollment heads toward its Friday deadline, which is likely to cause the website glitches and call center backups that customers have endured in past years.

It’s not clear how large the surge will be. According to the federal data, signups reached 3.6 million people on Wednesday. While the number is bigger than signups at the same time last year, the pace will need to increase in the remaining days to match the previous open enrollment signup total of 12.2 million people.