Interview at Google

Read this from somewhere...

A web-friend of mine just interviewed for a tech lead position at
Google. Here's a (slightly tidied
up and anonymized) version of their experiences:

Most of my work, at least at the start, should be in "production
software"--googlese for the software that helps keep Google's
amazingly huge distributed system running smoothly and seamlessly, and
is mostly Python though with ample helpings of C++ here and there and
a little bit of Java where integration is needed with some
Java-centric application server (e.g. to serve google-ads on sites
using such servers).

Plenty of "sideshows" doing such things as statistical analysis and
data mining on the huge wealth of data Google collects, maybe giving
[name deleted]'s team a hand in data-quality assurance, etc, etc.
Plus, every Google techie is supposed to use 20% of his time working
on his or her own pet projects which might become Google's
Next Big Thing---that's how gmail was born.

The selection process is grueling---multiple rounds of
phone interviews where they ask you (depending on the fields of
expertise you claim) everything from what's
2¹⁰, to how you would tweak bits in C to
find out if a machine's stack grows up or down in memory, all the way
to having you "program on the phone"... then all of a sudden they rush
you to Silicon Valley and you get a long full day of nonstop
interviewing. I didn't quite ace mine because I hadn't thought of
cramming on TCP/IP fundamentals, so I didn't remember which bits are
on in the three packets of the handshake (it's SYN,
SYN+ACK, ACK---I could have worked
it out, but not jetlagged and after about 6 hours' interviews ;-).

I made up for that when they had me program at the whiteboard a C++
implementation of unbounded precision multiplication; I did a
test-driven implementation of the trivial routine with
std::vector<digit> containers, then did some
handwaving about the Karatsuba algorithm (far too hard to implement
standing up at a whiteboard, of course ;-) and could sense I had
struck lucky... The guy interviewing me at that time had never really
done unbounded precision computation work (at least not implementation
of high-quality libraries for it), so by just opening the door a crack
to the huge and mathematics that underlies that field (in which I had
the good fortune to dabble a bit -- a byproduct of my interests in
combinatorial arithmetic) I had apparently exceeded expectations.

Lots of back-of-envelope computation and the like, too. A friend
of mine thought he was doing well in his second Google phone interview
when asked to sketch a way to compute bigram statistics for a corpus
of a hundred million documents---he had started discussing
std::map<std::string> and the like, and didn't get
why the interviewer seemed distinctly unimpressed, until I pointed out
even if documents are only a couple thousand words each, where are you
going to STORE those two hundred billion words---in memory?!
That's a job for an enterprise-scale database engine!

So, at least as far as the interviewing process goes, it seems
designed for people with a vast array of interests related to
programming, computation, modeling, data processing, networking, and
good problem-rough-sizing abilities---I guess Google routinely faces
problems that may not be hugely complex but are made so by
the sheer scale involved. I can just hope the actual day-to-day work
is as interesting, fascinating and challenging as the interviews
were---but from all I hear, it probably is. And they have bar-quality
espresso machines in rest areas... ;-)