We did a small experiment to see how a full scan of the Redis keys on
gitlab.com speeds up as we increase the batch size. The values on the
right are time in seconds for a full scan (no delete operations).
count: 10); 284.500529021
count: 100); 86.21216934
count: 1_000); 60.931676195
count: 10_000); 60.96355610
count: 100_000); 62.378172541
It looks like 1,000 is a good number.