This philosophy, all queues have explicit tuned limits with a drop log and increment a metric on queue full, was used thoroughly at AOL in the 90s. It worked very well, and let us use hardware at much higher loadings than is popular currently. Our goal was ~90% CPU at peak (systems I have worked with more recently start to die around fifty percent). Also of course there was a meeting each Friday to look at all queue depths and queue latencies and to see where we needed more capacity coming up. We did have so many subscribers that traffic was fairly smooth over all.