High demand for self-referred PCR tests means the HSE website is running out of slots in seconds by day and crashing at night.
While PCR test slots in Dublin released by the HSE during the daytime don't go unfilled for more than 20 seconds at the moment.
That's according to the developer of a web app which sends out alerts for open appointments.
The HSE insists most people who want an appointment can get one - but the executive admits appointments "may book out".
It's as the Chief Medical Officer has urged people to avoid crowded shops due to the spread of the Omicron variant of Covid-19.
Dr Tony Holohan says the strain is accelerating rapidly - and that everyone should consider themselves potentially infectious.
Just under 16,500 cases were confirmed yesterday - a new daily record.
William O'Connor, who first set up the system to try and book himself in, says the HSE website clearly can't cope with the traffic it's getting every night.
"It's kind of sporadic the way they're released - a couple of thousand seem to come out pretty much on the nose at midnight. I think the HSE website gets a lot of traffic at that time.
"This bot - that essentially sends requests to the website to see if an appointment is available; sometimes it takes a lot longer for the bot to get a response back, which tells me the site is under quite a bit of load.
"This is probably people trying to get appointments themselves, which is ultimately causing the HSE website to either slow down or essentially become non-responsive."
