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Lorri Dent
I pulled this chapter together from dozens of sources that were at times somewhat contradictory. Facts on the ground change over time and depend who is telling the story and what audience they're addressing. I tried to create as coherent a narrative as I could. If there are any errors I'd be more than happy to fix them. Keep in mind this article is not a technical deep dive. It's a big picture type article. For example, I don't mention the word microservice even once :-)
Given our discussion in the What is Cloud Computing? chapter, you might expect Netflix to serve video using AWS. Press play in a Netflix application and video stored in S3 would be streamed from S3, over the internet, directly to your device.
Another relevant factoid is Netflix is subscription based. Members pay Netflix monthly and can cancel at any time. When you press play to chill on Netflix, it had better work. Unhappy members unsubscribe.
The client is the user interface on any device used to browse and play Netflix videos. It could be an app on your iPhone, a website on your desktop computer, or even an app on your Smart TV. Netflix controls each and every client for each and every device.
Everything that happens before you hit play happens in the backend, which runs in AWS. That includes things like preparing all new incoming video and handling requests from all apps, websites, TVs, and other devices.
In 2007 Netflix introduced their streaming video-on-demand service that allowed subscribers to stream television series and films via the Netflix website on personal computers, or the Netflix software on a variety of supported platforms, including smartphones and tablets, digital media players, video game consoles, and smart TVs.
Netflix succeeded. Netflix certainly executed well, but they were late to the game, and that helped them. By 2007 the internet was fast enough and cheap enough to support streaming video services. That was never the case before. The addition of fast, low-cost mobile bandwidth and the introduction of powerful mobile devices like smart phones and tablets, has made it easier and cheaper for anyone to stream video at any time from anywhere. Timing is everything.
Building out a datacenter is a lot of work. Ordering equipment takes a long time. Installing and getting all the equipment working takes a long time. And as soon they got everything working they would run out of capacity, and the whole process had to start over again.
The long lead times for equipment forced Netflix to adopt what is known as a vertical scaling strategy. Netflix made big programs that ran on big computers. This approach is called building a monolith. One program did everything.
What Netflix was good at was delivering video to their members. Netflix would rather concentrate on getting better at delivering video rather than getting better at building datacenters. Building datacenters was not a competitive advantage for Netflix, delivering video is.
It took more than eight years for Netflix to complete the process of moving from their own datacenters to AWS. During that period Netflix grew its number of streaming customers eightfold. Netflix now runs on several hundred thousand EC2 instances.
The advantage of having three regions is that any one region can fail, and the other regions will step in handle all the members in the failed region. When a region fails, Netflix calls this evacuating a region.
The header image is meant to intrigue you, to draw you into selecting a video. The idea is the more compelling the header image, the more likely you are to watch a video. And the more videos you watch, the less likely you are to unsubscribe from Netflix.
The first thing Netflix does is spend a lot of time validating the video. It looks for digital artifacts, color changes, or missing frames that may have been caused by previous transcoding attempts or data transmission problems.
A pipeline is simply a series of steps data is put through to make it ready for use, much like an assembly line in a factory. More than 70 different pieces of software have a hand in creating every video.
The idea behind a CDN is simple: put video as close as possible to users by spreading computers throughout the world. When a user wants to watch a video, find the nearest computer with the video on it and stream to the device from there.
In 2007, when Netflix debuted its new streaming service, it had 36 million members in 50 countries, watching more than a billion hours of video each month, streaming multiple terabits of content per second.
At the same time, Netflix was also devoting a lot of effort into all the AWS services we talked about earlier. Netflix calls the services in AWS its control plane. Control plane is a telecommunications term identifying the part of the system that controls everything else. In your body, your brain is the control plane; it controls everything else.
In 2011, Netflix realized at its scale it needed a dedicated CDN solution to maximize network efficiency. Video distribution is a core competency for Netflix and could be a huge competitive advantage.
The number of OCAs on a site depends on how reliable Netflix wants the site to be, the amount of Netflix traffic (bandwidth) that is delivered from that site, and the percentage of traffic a site allows to be streamed.
Within a location, a popular video like House of Cards is copied to many different OCAs. The more popular a video, the more servers it will be copied to. Why? If there was only one copy of a very popular video, streaming the video to members would overwhelm the server. As they say, many hands make light work.
Right now, up to 100% of Netflix content is being served from within ISP networks. This reduces costs by relieving internet congestion for ISPs. At the same time, Netflix members experience a high-quality viewing experience. And network performance improves for everyone.
What may not be immediately obvious is that the OCAs are independent of each other. OCAs act as self-sufficient video-serving archipelagos. Members streaming from one OCA are not affected when other OCAs fail.
Design
As an avid Netflix user, I've used the service on the Xbox, PlayStation, Netflix's Web site, Android phones and tablets, and the iPad. On all of those devices, Netflix looks roughly the same, with one main screen that shows rows of movies and TV shows with only the videos' artwork. To find a video to watch, you swipe left and right through those rows.
Coming from that horizontal setup, the Netflix for Windows Phone design slowed me down. Instead of those rows, movie and TV show titles are shown in a list with the video's name, the year it aired, its Netflix star rating, and its movie or television content rating (such as PG-13 or TV-14). All that information on the screen makes the Netflix app look cluttered, and because you have to scroll up and down to look for videos, the app is tedious to navigate.
You can use the app entirely in landscape mode, which makes it feel less cramped and easier to use, though I'd still rather the app used the standard Netflix design and let me scroll horizontally through movie and TV titles.
My other issue with the app's layout is that if you scroll down too quickly, before the app has a chance to load each section, the app will jump back to last section it loaded instead of letting you continue scrolling.
Getting around
To use the app, you must sign in to an existing Netflix streaming account, which costs $8 monthly. You can't sign up for a new account in the app, something you can do in the iOS and Android Netflix apps.
Once you sign in, you'll see the home screen, which shows your most recently watched titles and the videos Netflix suggests based on your viewing history. All of the typical Netflix-suggested genres based on your viewing history are present, such as "because you watched Mad Men" and "movies featuring a strong female lead."
At the top of the home screen, you can quickly finish watching a video that you started in the app or elsewhere on Netflix by tapping the resume button next to the title of the video. TV shows will only show the episode name, which can get confusing if you don't know which show you watched last.
One last left-swipe shows your Instant Queue, a list of videos you want watch eventually. You can add any title to your instant queue from anywhere in the app by tapping the video's title and touching the Add to Instant button.
I found the Netflix app was slow in two instances. First, it's slow to start up when you first open it because it needs to establish a connection before it loads the list of videos. It's worth noting that if you don't have connection, the app won't load past the first red Netflix screen.
Playing video
If you tap the show or movie's art anywhere in the app, that video will immediately begin playing. If you tap the video's name instead, the app brings up a synopsis, the Netflix community's average rating or your personal rating, actor and direction information, and a button to add it to your instant queue.
When you play a video, you can tap the screen once to show the progress bar, Play/Pause button, and caption options. If you hold and slide your finger over the progress bar, you can jump back or ahead to different scenes. Just like in other versions of Netflix, the app shows still images of each frame to help find the right spot.
Video playback was pretty good, but even on CNET's Wi-Fi signal, the picture was choppy and pixelated before it fully buffered. Once the video had loaded completely, it looked clear and didn't freeze.
Final thoughts
Across its many mobile, media player, and console apps, Netflix looks nearly the same. But that unifying design goes out the window with the Netflix for Windows Phone app (no pun intended), which is cluttered and laborious to get around in.
However, once you get past the clunky navigation, the Netflix app lives up to its purpose of helping you find and stream videos, and manage your instant queue. Even if Netflix never refreshes its Windows Phone app to be easier to use, it's still worth downloading so that you can stream videos wherever you go.
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