More specifically, what are the logistics of handling thousands and thousands of DVDs at Neflix HQ? I realize that there are multiple regional centers, let’s just talk about what’s going on at a particular center, and leave aside the occasional need to ship something from a different center.
I am mailing back my current DVD today. They will receive it tomorrow. A machine will open the envelope and extract the disk in its bar-coded sleeve. A scanner will read the bar code and identify the disk, then the computer will say “twicks had this, let’s assume she’s the one returning it.” The computer then credits my account with the return and cues another program to send me the receipt confirmation email.
Then what?
The physical disk goes … where? Does the stream bifurcate immediately, into “this is at the top of someone else’s queue” and “this can go back onto the shelf”? Do they actually check queues at that point or do they have an algorithm indicating relative popularity? (Recent releases of popular movies obviously get a lot of action – some of my beloved '40s musicals presumably don’t.) For DVDs that are “shelved,” I assume that’s also done by machine – is there a way of storing them so that the bar codes can be read easily to find a particular disk when the next request for it is made?
For now, let’s assume that the disk I’m returning is a popular one that goes into the “going out today” stream. Say there are 25 people who have this disk at the tops of their queues. How does the computer pick which one of those people gets it? Is it based on which of their returned movies gets processed first? (e.g., Member A’s return was processed at 7:00, Member B’s at 7:02, Member C’s at 7:04, so they are assigned the specific disks that reenter the stream at 7:01, 7:03, and 7:05 respectively.)
Leaving aside how the system finds my next DVD, once it’s found it, what happens? It addresses an envelope to me, but the only coding on the exterior looks like USPS coding, not Netflix coding. There’s the window in the back through which it can read the bar code, but how do they know that the DVD has gone into the right envelope? Presumably it’s about collating two queues, one of disks and one of envelopes, into each other – but if there’s a hiccup and the queues get out of sync (two envelopes stick together, e.g.), you could fuck up a whole lot of orders before that got caught. Does the USPS address code provide enough info to be specific to a particular member?
At that point, it’s all pretty straightforward – the “we’re shipping X today” email goes out and the physical envelope goes into standard mail sorting machinery that reads the USPS codes, and off it goes, to be delivered to me 48 hours after I’d sent back the first disk.