I am writing this post as I think it might be useful for other Canvas-users, but I am also interested in hearing others experience with courses with large amount of students and groups.
We are planning to have a MOOC for norwegian teachers. There will potentially be tens of thousands of users in one course. We were thinking of splitting the students in small discussion groups, f.ex. one for each school, in which they
self register. I tried creating a couple of thousand groups in a test course. I named the groups "Studiegruppe nnnn", where nnnn is a a number from 1 and up. Then, as a student, I went into /groups for the course. I started searching for the substring 178 to see how fast groups containing that substring would turn up. It took a lot of time, as can be seen on the enclosed video, and to my surprise it looks like Canvas does the search on the client side by downloading groups ten by ten, as is shown in the network inspector in the video.