I don't think they're saying it crashes. They're suggesting that they have buffers of data that fill up during periods of high load, and when those buffers get

I don't think they're saying it crashes. They're suggesting that they have buffers of data that fill up during periods of high load, and when those buffers get full they have to drop any new incoming requests until the buffers get flushed to the database. During that period of time the site becomes unresponsive.