user_bulk_download isn't efficient enough to succeed in 30 seconds (default max_execution_time) here. Apparently it does two DB requests for each user (one in the user_download_$format and one in profile_load_data), which results in 13.2k queries for the 6629 users that we have on the instance that fails here.

The temporary workaround is to set: php_admin_value max_execution_time 240

(2-3 minutes is what it takes still).

Isn't it possible to do it in one or two queries (eventually paging per 1000 users to not get too huge answer arrays)?