It's because GCs are starting to take a long time now that there is so much stuff to keep in memory.  Items are lazily loaded, but they never get unloaded.  Eventually (after a day or so) crawlers drag everything into memory, and GCs take excessively long. I plan to fix the problem by starting to dump stuff back out of memory. In the meantime I just restart HN when it's starting to spend too much time GCing, which in effect dumps everything out of memory except the most recent 15k items.