How much bandwidth does YouTube consume daily and monthly and how much does it cost?

This is not something new, as Wired article linked in the question seems to imply. Big providers and CDNs have specific terms and conditions for interconnection that involve little or no cost for direct settlement of traffic. It's a matter of network optimization which lies at the core of the Internet and allowed its costs to be substantially lower than any other network in the world. A little bit of logic helps to explain. Small ISPs pay to bigger ISPs to have their traffic routed all around the world. This is called "transit" and is the most popular arrangement for interconnection between ISPs. Small (local) ISPs pay transit to bigger regional ones, which in turn pay transit to national backbones, and so on. However, as you go up, who would the bigger ISPs connect to for transit? The answer is simple: instead of paying for someone even bigger, they interconnect between themselves, using what is known as a "peering" agreement. Let's assume that you are one of the biggest ISPs in the world. You would like to sell transit to YouTube, but a competitor already did. Now your competitor has much more traffic than you have, and he wants to start to charge you for this traffic. It's easier and more efficient for you to connect to YouTube for free than paying someone else to do it for you. At this point YouTube has so much traffic, and Google as so much fiber, that they are able to negotiate such deals and interconnect with any ISP in the world. In fact, most of them are dying to connect freely to YouTube, because it means saving a lot of money. That's good for everyone involved: ISPs, Google/YouTube, and the user, who gets better performance for a lower price.

As a general rule for all these types of interview questions break them into smaller and smaller pieces so it's a manageable problem to solve. Then add things back up. So for instance on this question I would probably first break 'store' and 'serve' into separate problems. You'll also need a few inputs like. Over what period of time. What inputs will they give you like: # of videos, growth rate, users? For anything missing you'll need to come up with an estimate of that. Then I'll break each branch down to its component parts, so for example on the on the 'store' part of the tree I'm thinking about things like the following: How big is an average video? Or maybe video storage per user? How much video will you have, now and growth rate? (or users if you went that route) Can I just keep it all in one place or do I need to replicate some content elsewhere, which introduces CDNs How much does it cost per unit of storage, perhaps TB. What other equipment is needed for storage? Do I need to get into problems like indexing and the smarts of serving it? Sometimes in these questions they want to see how detailed you can get in the tree, so even the above bullets can be their own estimation sub exercises. Sometimes they really want a number so you'll need to make some assumptions in various areas to simplify the problem. For example you may elect to ignore geographic replication, that's potentially a very complex branch of the tree.

My estimations: 1) Youtube has abo ut 400M monthly active users 2) Every user spends about 1/3 hour daily viewimg youtube video => 10 hour monthly 3) 400M * 10 hour = 4B hour monthly streaming 4) month has 30 * 24 hours = 720 hours 5) from 3 and 4 we can consider that there is 4B / 720 = 5.5M simultaneous streamings at any given time. 6) for 500 simultaneously streaming page one needs two medium sized dedicated servers (back and front) about (350$ with network cost) assume 15% is hosting income so if you host yourself it will cost 300$ 7) for 5.5 M cost for simultaneous serving will be 300  * 5.5M /500 = 3.3M $  monthly for streaming 8) Storage cost is about 10 - 15% of streaming cost so storage cost will be 3.3M/100*15 = 400K 9) whole cost will be about 4M $ monthly

This is more of a question to see how you think rather than coming up with the correct results. So, an algorithmic, problem-solving mind would go with the following thoughts: 1. The world has around 7 billion people 2. I know that 1 billion of them are connected to the internet 3. Youtube is pretty popular. I would assume that 70% of all internet users are using it. This is 700 million people users. 4. On the internet, usually around 4% of visitors are contributors. This would make around 30 million users who upload videos. 5. If the average user uploads 1 video per month, this is around 350 million videos per year. Youtube is there for some years, so there might be 1 billion videos in total on youtube. 6. If the average size of each video is 2 MB, then the total storage needed is 1 billion times x 2 MB 7. The average cost of storage with 99,99% availability is Y cents. 8. So, the total cost would be around 2 billion times x Y cents

There are two components in the question that you have to address, storage and distribution of content.StorageBased on the available data, there is roughly 24TB of data uploaded daily to YouTube (http://blog.pexe.so/what-youtube-looks-like-in-a-day/). Those are just the original videos. YouTube generates many different profiles (different quality and size) for each video [well, it is generated based on the demand for a particular profile]. For our calculations we will consider the size of each original video uploaded to YouTube to be quadrupled by all additional profiles.24TB * 4 * 365 (days in a year) = 35PB of data.As we can estimate that a little bit more than 110M videos is uploaded every year and there are some signs that YouTube contains over 1B videos, YouTube needs to store roughly 350PB of videos.We could count how much YouTube would pay for the disks directly, but we need to also count servers electricity and others, so we can use https://cloud.google.com/products/calculator/ to estimate all the costs we need.Lets calculate how much would cost YouTube to store 500PB of data annually on GCP Roughly $164M. Content distributionThe question is How much it would cost to serve all YouTube videos. If we will serve the videos only once, the answer is very straight forward. Based on https://cloud.google.com/interconnect/cdn-interconnect#pricing we know that a GB of data cost at max $0.06. 500PB * $60,000 = $30MIf we want to try to estimate how much it costs YouTube to run their CDN network, we need to consider some additional inputs.YouTube is very secretive about the real numbers, but based on https://www.youtube.com/yt/press/statistics.html "every day people watch hundreds of millions of hours". Lets assume people watch 100M hours of content a day. It is not hundreds of millions as they claim but seems like that's actually closer to the reality. Based on the infographic http://blog.pexe.so/what-youtube-looks-like-in-a-day/ an average video is 15 minutes long and represents 86MB of data.((100M [hours] * 60 [minutes]) * (86MB / 15 [minutes]) = 32PB/day = 960PB/monthOnce again, based on https://cloud.google.com/interconnect/cdn-interconnect#pricing to stream 1GB of data costs at max $0.06. 960PB * $60,000 = $57,6M/monthWe are still missing the infrastructure, but this is considerably way more complicated that to calculate the storage or distribution.

Well, the bitrate for 1080p video on YouTube varies from 3,5 to 8 Mbps. So, let's assume an average of 5 Mbps. For 60 seconds, that's 300 megabits, or about 37 MB. In 2012, in an article that attempted to answer http://www.forbes.com/sites/quora/2012/10/29/how-much-did-it-cost-youtube-to-stream-gangnam-style/, Forbes magazine estimated that YouTube probably pays about $0.01 per GB, so 0.037 GB * $0.01 / GB is $0.00037 -- about a penny for every 50 hours of video streamed (not including the cost of storage, hardware, electricity, etc. -- just bandwidth).

Google has published  how much bandwidth you need and for the highest performance HD speed they recommend 18Mbps (mega bits per second). Most online HD applications are 720P at 30 frames per second that need up to 4 Mbps.Watching a movie on your computer willing to compromise some quality you can do well with about 1 Mbps.You can check more specifics at: https://support.google.com/youtube/answer/2853702?hl=en&vid=1-635805265762403931-3047912769

It is very difficult to ascertain without any a prior information from Google on the network connectivity of YouTube, etc.  as to how much bandwidth YouTube consumes daily. Many people do not know this, but Google has their own AS Number and has direct private peering arrangements with almost all the ISPs worldwide. (See my answer on ). Caching (which includes YouTube caching) would not reflect on the bandwidth usage that Google would otherwise measure on the YouTube peering edge (if we can assume one). So, for example, in a geographical location X a Sherlock Holmes II Trailer may be downloaded 3-4 times from YouTube, but then the edge cache will probably come into play at that specific geographic POP and keep serving that video and not from YouTube's server farm.

If you are asking how much data Youtube video then it depends on the video quality you are watching in.For example, a 480p video will use 5.50 mb/min. I've done test for all the Video Qualities (240p, 360p, 480p, 720p, 1080p).  You can see the results at http://www.clifftam.com/much-data-youtube-video-use/ . If you are asking this to find out how much data you need to have, then use the results from the link above and figure out how much Video (in minutes) you will be watching on a monthly basis.For safe bet, always watch them in 480p (this is the default video quality).  720p and 1080p (high definition) will eat up your bandwidth like there's no tomorrow.