Associate product manager interview questions shared by candidates
What is the marginal cost of a gigabyte in gmail?12 Answers
I had no idea what marginal cost is but after a lot of hints, I finally came up with 1$ / a gigabyte though that's probably on the low end. The right answer is probably a bit higher, say 2-3 $ / a gigabyte (from the costs of servers, disk space, maintenance, set up of servers, maintaining webpage, designing user interface and then offset by the advertisements and click-throughs)
probably even less than that now. http://thenextweb.com/2009/11/11/data-quarter-price-googles-plan-chrome-os-storage/
Isn't marginal cost the cost to produce an additional unit? So costs like designing the user interface, maintaining the webpage (which would have to be done no matter the gigabyte capacity) shouldn't be accounted for.
Ah, you clearly would have made a better candidate than I have. Like I said, I didn't know what marginal cost was so I just came up with a ballpark figure.
Here's my guess at what they're looking for. Marginal cost - this is the additional cost for adding a user. It doesn't need to take in to account the software development effort, but it should take out the atomized cost for everything else. You need to price out the the cost of the enterprise HD/GB. We can call it $1 by GB. Then you need to realize that there needs to be redundancy, so at the lest we need to double that number, if they put a super high value on data retention triple it. Then you need to think about server cost and divide that out, server rack space cost and physical rack area...etc. So if it's $1 for the actual HD space it's probably more like $2.50-$3.50 for the total marginal cost. I don't work for google, but my guess is that they're looking at the though process. What will change with a marginal user increase and what will not. If you only think of the cost of the HD then you're not getting a job with google.
The simplest answer is to look up the Amazon S3 costs (currently platoing at 5.5c/GB) and assume that the economics are fairly similar.
To correct my own post - these are per/month prices. So the eternal retention prices would be ~50 times higher, which gives us the same figure as Jon's.
Considering the money they make per account signed up with gmail, I'd say they definitely make money per gigabyte spent for gmail, but I'm not sure how much.
I never worry about the capacity of my gmail account, it seems to me the cost of an extra gig of gmail storage is zero. As it is the mission of Google to make sure every users always have enough storage capacity and Google is doing a great job in this area, so the maginal cost of a gigabyte in gmail should be zero.
If it was a cost, Google would not exist. When analyzing costs, and especially marginal cost, one must consider all aspects. Once one considers the return too, the cost goes into a negative
The marginal cost of adding a gigabyte is either zero or thousands of dollars.. Either the gigabyte is already physically in existence or you would have to build a new server. The marginal cost is not averaged across all gigabytes. There might be a minor increase in energy consumption due to this extra gigabyte, but who will notice that? If your goal is to stand out in an interview, I would suggest going the Thousands of Dollars answer. For those non computer guys out there, let's relate this question to something physical.. What is the marginal cost of adding one more person to an airline flight.. Their are two situations, the plane in not already full so we can essentially neglect the cost of the additional passenger since it is so low.. (The extra energy to move the 200 pounds, when the plane is already moving hundreds of thousands of pounds, and the 25 cents for a soda..) But if the plane is already full, then the marginal cost of one extra passenger is the cost to fly a second plane.. Thousands of dollars...
Marginal cost is the cost of adding one additional unit, so fixed costs of Gmail are already taken care of. So the cost is the cost of the hard drive + any labor to install and configure that hard drive for gmail. Take a sum of the costs and then divide it by the size of the hard drive (GB) and you should have your rate. I think it will be well below a dollar. In my quick math I had it at 20 cents but that assumes consumer pricing.
Why is a good user interface good for the company?3 Answers
I talked about how a good user interface will encourage users to stay on the page longer, retrieve their information easier and make it more likely that they will click on ads that they feel are relevant. They will also convince other users to come to their product if it is well built.
For a company like Google, the UI *is* the brand. It's the point of communication with the user -- so a good UI saves a whole lot of money off advertising.
A good UI directly reflects that the company represented has put in adequate amount of (1) end-user targeted research (2) in-house thought process (3) identified end-user needs to be addressed via the UI The initial popularity of Google Search was the fact that (a) the UI was simple & straight forward (b) segregated ads / sponsored links from actual search results (c) displayed the time required to generate the search results (d) being all the above was the fastest loading search result page
How many ping pong balls fit in a school bus?3 Answers
There's a few things I would clarify with the interviewer before starting but I'll spare you for now. Let's start with the size of the balls, that we assume will have a radius of 2cm. To account for the gap between balls when filling a space, we will also assume that the balls take up the space of a 4cm x 4cm cube (16cm3). At the end we will also add an extra ball for every 4 balls to account for the gap neglected in assuming a cube. To keep things simple, we assume we have nothing inside (no seats, etc). In guesstimating the dimensions of the bus we'll say each seat would be 3.5ft long while the center aisle is 1.5ft for a total width of 8.5ft. We'll also guess that a bus is about 40ft long and 8ft tall. This brings our net volume to: 2,720ft3. 1ft ~ 30.5cm 2,720ft3 ~ 77,021,823cm3 77,021,823cm3 / 16cm3 ~ 4,813,864 balls Accounting for gap: 4,813,864 / 4 ~ 1,203,466 balls Net total: 4,813,864 + 1,203,466 = 6,017,330 balls
Another ridiculously detailed answer can be found at > http://www.nab.bz/bus-explanation.pdf This is not my work, just found it while preparing.
Assumptions: Big school bus, windows closed and empty Deduction Number of ping pong balls that can fit = vol of bus/vol of ball vol of school bus = L*B*H =8 * 70 * 10 ~=6000 cb . ft B= two seats on each side and each seat is about 2 feet wide, so ~ width of bus = 4+4+2 =10ft L = 20 rows + Entrance + Driver seat = ~25*3 = 70 ft H = 8 ft Volume of a Ping pong balls = sphere=4/3 pi r3 =4 cb. inch But Vol df sphere doesn’t matter unless we use the inside volume of the ball. So we can find the volume of sphere when the balls are stacked efficiently by adjusting height for the gaps. Volume of cube = L B H = (diameter of ball * diameter of ball * adjusted ht of sphere) = 2 * 2 * 2.5 = 10 cu in ~= 12cu in = 1/144 cu ft 1 cu ft = 12 * 12 * 12 1 cu in = 1/12 * 1/12 * 1/12 6000 / (1/144) = 60*144 = 864000 balls
How would you design google maps?2 Answers
This question was a bit of an open ended question. We could go as low or as high in detail as I wanted to go. I chose to go a somewhat inbetween. This was probably the hardest question because I didn't really have a good idea of how it was built or what was the underlying technology underneath (don't memorize this, my interviewer said it was actually better that I didn't know so that we could discuss it). I believe what I said was that the maps would have some sort of graph data structure underneath (i think that makes the most logical sense) and that things like locations would be vertices and edges would be all the roads. After that, my memory gets a bit fuzzy but I remember talking about things like how would I speed things up? What's going on behind the scenes when people are dragging their location ? After a bunch of hints ( you can already tell that I was a bit lost), I said things like caching would make things faster, you can cache the data structures of your location on your computer instead of retrieving it from the server, when you drag the map around, basically you compute the vector of where your mouse is going and then retrieve each image in the direction of the opposite of your vector.
Since this question was directed at a product manager, presumably the interviewer was looking for a marketing answer. For example, you want a flexible user interface because there are so many types of queries which are location-dependent. And then you want to think about relevant content (emphasis on ad value) which you deliver to queries, depending on how much information is in the query and what the location maps to (and whether user is mobile). There's a paradigm from navigation systems - let users customize which types of businesses they always see on maps.
Design an elevator for a building (no specifics on what kind of building). Follow up design with two elevators and etc.2 Answers
User interaction requirements: + Aluminum and stainless steel materials/colors. + Big, bright light on ceiling. + Tactile screen with braille bumps on the sides of the tactile buttons for floors. (Accesibility) + Sound floor notifications. Efficiency: + Elevator serves users on a first-come first-served basis. Linear queue. + Gives priority to direction (up or down) indicated by current user. Other: + If floor button pushed until elevator door closes, fast mode is activated. Goes directly to desired floor without stops. (Already implemented in most elevators around the world for emergencies and fast access for local authorities). --- Extension to two elevators: (this would be a problem of concurrency) + We have a single queue with two consumers (two elevators). Elevators serve petitions on two criteria: priority of first-come-first-served and proximity of each elevator to desired destination. Final priority of petitions is based on these two aspects.
For any of the questions that start with "how would you design a..." - start with clarification of the CLIENT's NEEDS and context. Example: "how would you design an elevator?" I would first want to know more about who would be using the elevator and why. What is the purpose of the building - then go from there. The building might be a 6 story parking garage that sees high volumes of traffic at the beginning and end of the business day. The building might be a 6 unit condominium complex, a hospital, or even a furniture warehouse. Each of these types of buildings will have very different types of people/uses and therefore different requirements for an elevator.
How can I get to some gold in the middle of the amazon in the cheapest way possible?5 Answers
Use GPS and wind power and sail.
Partnering with an indigenous tribe in the area. They are the ones who have better experience about the terrain, routes, and possible hazards. Using their transportation technology but a Western-style portable navigation system.
outsource to india.
Light a match and hope the wind blows from the right direction.
Send some there. The question does not ask how to get in out of the Amazon.
What are three long term challenges facing google?3 Answers
Three potential long term challenges facing Google are: 1. The propensity for people to become immune to PPC ads. This could happen either because people find them less relevant or because they pose as an annoyance on the screen. 2. The transition from keyword search to "conceptual" search or other competing technology that results in a more precise solution to the consumer's needs. 3. The top two, combined with an overall loss of "search" users substituting affiliate technologies such as YouTube to find the information they need more readily and more easy to consume.
I think this answer should be given on a broader strategy perspective, and not strictly concentrated on details. However that's just up to personal opinions. In my opinion, three potential long term challenges for Google are: 1. The increasing success of Facebook and its related services, as well as their partnership with Bing. Reports show that Facebook plans to implement a search engine. Whether this search engine would be developed solely by Facebook or in partnership with Microsoft is irrelevant. It would dramatically affect Google numbers, since millions of users would start searching directly from Facebook's social network. Solution: only solution is to increase influence in the social networking atmosphere. For instance, acquiring Path and boosting Google+, joining both of them for an added-value user experience. 2. Market diversification. Google, as most tech companies, started with one product and then diversified their product catalogue. Many companies have failed in their diversification. By diversifying in a wide range, many of them have failed in multiple fields and achieved success in none of them. On the other side, other companies haven't diversified enough and this situation has provoked huge sale losses (ex. Cisco). Solution: Google needs to continue its diversification rhythm but not forgetting the end user's thinking style. Tech diversification involves creating an atmosphere in which all products are in the same style, using the same platforms. (namely, Apple products). (Counter-example: Microsoft products (although they've realized about this not a while ago and things are slowly changing in that sense). 3. Google's influence in the entertainment and multimedia industry. As part of Google global strategy, they have increasingly tried to diversify into the entertainment industry. Sadly, there is still a long way to achieve success in this field. Google Music is a growing platform but its numbers are not comparable to other services such as Spotify or iTunes. Solution: acquiring Spotify. In the TV aspect, Google TV cannot grow at its fullest potential while depending on SONY devices Logitech boxes. Reports show that cable and satellite customer numbers are going down in favor of online services. Solution: implementing a portable platform runnable on the Chrome browser and on other devices such as Sony Playstation 3, with partnerships with content providers. Possible partnership or venture with Hulu would be suitable.
In my opinion the 3 key challenges for company like Google, which is immensely focused on innovation, solving problems related to internet and has the mission to manage world information would be... 1) Culture: With its ever expanding reach in terms of # of employees, locations, offices, teams, products and services how Google make sure to continue maintain the culture of first of all HIRING the right people and then making sure the INNOVATION doesn't die down. There are only so many smart creative people in the world or only so many can be made to adopt that thought process. DNA of Google is innovation, smart people and think BIG (10X), which I think is crux of its success. 2) Diversification: Striking the right balance between how much to diversify in product lines and how much to control. Google is moving or has moved into into robotics, android, mobile phone, laptops, cloud, computer engines, solar, energy, internet, cars, google glass, artificial intelligence, wedding planners, social media and many more. The key point is how to keep control of all these product lines and also to understand how they will help Google achieve its mission. 3) Competition: Facebook, Twitter, Microsoft, Baidu, DuckDuckGo, etc. are posing competition and coming from all directions. Google will be devise a strategy on how to maintain its lead in SEARCH space, advertising space and other revenue sources. Sundar Pichai is new head of almost all products except YouTube, so it would be interesting to see what are the next BIG things Google will come out with.
walk me through your career history1 Answer
not sure this is a good use of interview time, when it's already been asked by the screener and interview slots are 30 mins each.
Tell me a Joke.1 Answer
This came out of the blue, and I think I chose a good one. This does seem quite cliche though. I get why he asked (trying to get a read on my personality) but frankly ts a stupid question.
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