It's fast because it's not bloated. It returns fairly minimal (if not elegant) HTML, and loads few additional resources.
The HN front page is about 7kB - many times smaller than even minimized jQuery (83kB as of 2.1.4).
The data is small and all fits in RAM on a single server during normal operation, so there's no additional network latency hitting a DB over the network.
On Hacker News, the ask and show pages are implemented just like the front page, but they filter the item list based on title or whether or not there's a link.
And yes, that means they won't show items not already loaded into RAM ;)
The Hacker News codebase is in Arc, and will be for the foreseeable future. All the core domain work is done in it, and we write Arc code every day. When it makes sense for performance or practical reasons we call into Racket, but not frequently enough that we've even bothered exposing nice syntax for it (like anarki's $).
Now running on the new server. DNS may take a bit to update.
Things are running on the latest FreeBSD and Racket, but the code is way behind what I've been working on in HN, so please email me at nick@ycombinator.com if you see anything wonky.
We accumulate modified items and profiles by hooking save-item and save-prof. Then every 30 seconds or so we submit an update batch to Firebase using their REST API.
The biggest pain was fixing up Racket's HTTP libraries to support HTTP pipelining correctly and writing our own streaming JSON serializer than minimizes the frequency and lifetime of allocations.
This is my fun little side project - the aim being to get Arc running inside of Racket with a little less friction: better performance, profiling support and source locations for errors.
It can run some Arc code unmodified. You'll likely be more comfortable with rark/load (which defines everything at the top level, and is hopeless [1]).
Good error reporting is pretty disagreeable to me, lol. :-p
I think Arc's main advantages over Scheme, once all the Arc-like naming conventions and macros are in place, are setforms, defcall (not in pg's Arc), and the ssyntaxes (a:b c), a.b, and a!b. Going by the examples, Rark has setforms, and its ability to unwrap data structures using function calls indicates defcall wouldn't be hard to add if it isn't there already, but I don't see anything about ssyntax. I've been meaning to download and run Rark to see if ssyntax support is actually there after all.
The abstract "Scheme" I'm talking about might have a certain advantage over Racket, but I might just be doing it wrong: Is possible to write a macro and use it in the same file? I've had to break my utilities into three files just to have multiple layers of macros. I'm interested in seeing whether Rark makes this any easier.
It's currently missing extensible setforms, but all the standard ssyntax and brackets should work. They're detected and expanded (awkwardly right now) at the reader level.
It's hard to say since Arc doesn't have a formal spec. The end goal is for everything to just work like it would in pg's Arc. I'm slowly working toward that goal.
Right now, Arc s-exp editing macros are straight-up unsupported. In addition to pattern matching, you have to explicitly break hygiene with leak and bind:
"If you looked at it closely, I made many changes in the spirit of getting something running that PG (and you!) would likely not agree with."
I didn't see the repo while it was online, but I've always looked forward to Arc (or at least Anarki) becoming usable as a Racket language at some point, even if it were an awkward fit. Just how disagreeable are we talking, here? :)
