After reading another bug report about replying to large threads with the quick reply box I decided to merge many threads on my test import server so I can test out the authors report. What I found was the following: When merging around 20 small (ish) threads with less than a 1000 posts in each thread I would experience a gateway timeout. Looking into it I see that the timeout occurs due to the bundling of the merge threads and the replace into the XF search table. Could this be split into seperate requests? When merging around 5 threads with excess of 10,000 posts in each thread I simply get a blank page indicating PHP exhausted it memory. The logs confirm this, memory limit is set to 128MB. Not sure if they can be broken down into smaller pieces of work but thought it would be beneficial to document.