With the first World of Warcraft Classic stress test in the bag, developers have already announced the second, seemingly unplanned, event for Wednesday, May 29th from 2:00 pm to 4:00 pm Pacific / 5:00 pm to 7:00 pm Eastern. Anyone who participated in the May 22nd event is invited back for the one on the 29th.
During the first event, players experienced a number of issues that, according to Blizzard, provided the dev team with "valuable data" moving forward. As a result of persistent issues, devs "were not able to test other aspects that we'd planned for". These unnamed aspects will be front and center during next week's test.
Read more on the World of Warcraft Classic forum.