HN load times are kind of high compared to slashdot or reddit, I often just give up on waiting and got to a different place, so I may count as a hit. HN also gives me timeouts when I look through the first page and take too long to click on the next page link, which is why I tend to refresh the first page only, you never know when you will get into that state. HN definitely need some help in capacity and response times to compete with the big guys.
PURGE is probably never used (and in my 5 years of log analysis I have never seen it with any major API, but I am sure someone uses it, but why design for such a small fringe) and it is also not part of the HTTP (RFC-2616, section 9: https://www.ietf.org/rfc/rfc2616.txt) spec so why design for it, just asking for trouble; stick to 'modified'-type headers to control the cache and HTTP response 304 when needed.
While XML is ok, JSON is the dominant format for REST APIs and consumed by way more frameworks and libraries at this point.
Was this written 10 years ago, it seems kind of stale and confusing.
Things you should do before going live: load test obviously and monitor how memory gets used (if you hit swap you are too low of memory or mem consumption is too high and needs to be separated/load-balanced). CPU usage should be monitored and if you are going over 90% for a long duration you may be putting too much in one instance. Things like that, but from what I gathered your biggest flaw was not doing any load testing (jmeter, floor, etc, lots of tools to help you). I've been doing performance and optimization most of my web life (at least since 1992), you are not alone, people throw un-loadtested sites into the wild all the time and fail every time when slashdot/reddit/hn -effect occurs. But you can always do better now that you have learned from this failure.
Stick with Java, more job security, bigger support base, better tooling and Java is likely to go obsolete as I predict Xtend will very soon and Scala will soon after when people realize how much of a minefield that language is (I think they keep all those 'special' cases there to see if you were paying attention in class, no idea).
Java for the few oddities is quite a solid language and one that will make you marketable in the industry for many years. For personal projects... pick one that has the most verbose structure because 6 months from now you won't remember why you did something and having to figure out the language and logic is a bit annoying.
Video capture cards can already do this (http://www.newegg.com/Product/Product.aspx?Item=N82E16815100...) or just pay $8/mo to Netflix and stream it. The only reason for ripping Netflix streams is to view them on Linux since their DRM barely works on Linux through Wine which is not always ideal. If they got that DRM thing working on Linux, I am not sure there is a legit reason to rip content from Netflix, the monthly fee is very reasonable.