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Estimate the cost of storing Google Photos on the photos app.

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Clarifying questions:

 

  1. Google photos - an app that syncs automatically to your camera app and uploads photos to Google cloud and reduces the need to store it on your device

  2. Cost of 1GB storage $0.002

  3. Time storage cost per year

 

 

Equation: 

Cost of storage per year = average cost of storing photos per day x 30 days x 12 months

The average cost of storing photos = # of photos uploaded per day x average size of photos x $0.002/GB 

 

# of photos uploaded per day:

 

Photos from developed world + developing world + underdeveloped world.

 

Total world population 7B, 50% have access to the internet. → 3.5B. 

70% of those users use smartphones with camera and the majority of them are android users.  → 2.1B. 

 

Assuming 60% of these are android users → 1.2B Android devices that have Google photos app

Assuming 40% of iPhone users use google photos → ~300M iphone users use Google photos app. 

 

Thus we have about 1.5B total photos app users. 

 

Breaking down the usage of camera and photo upload by the market:

 

  1. Developed countries - Assuming users take around 10 photos per day on average with high end cameras. Average photo size 4MB. 

  2. Developing countries - Assuming users take around 5 photos per day with a medium to high end cameras. Average photo size 4MB

  3. Developing countries - Assuming users take around 2 photos per day with a medium to high end cameras. Average photo size 2MB

% of world in developed world ~ 20% 

% of world in developing countries ~ 60%

% of world in developing countries ~ 20% 

 

Assuming the same distribution holds across smartphones too:

 

Google photos users in  developed world ~ 20% → 300M

Google photos users in developing countries ~ 60% → 900M

Google photos users in  developing countries ~ 20% → 300M

 

The total size of photos stored per year:

 

  1. Developed - (300M x 10 photos/day x 4MB x 30 days x 12 months)--> 4.3 x 10^18 Bytes

  2. Developing - (900M x 5 photos/day x 4MB x 30 days x 12 months) → 6.4 x 10^18 bytes

  3. Under developed - (300M x 2 photos/day x 2MB x 30 days x 12 months) → 0.4x10^18 bytes

 

Total storage ~12 x 10^18 bytes -->12 x 10^9 GB 

 

Total cost → 12 x 10^9  x $0.02 → $24 x 10^7 → $240M

 

This would be the cost for just one data center, assuming Google has atleast 5 data centres where this data gets replicated, it will be close to 240M x 5 --> $1.2B!

 

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Things you did well

  • Described the formula in the beginning: You listed the high level formula in the beginning which is great and makes it easier for the interviewer to follow you throughout the calculation   
  • Breakdown of users: I like how you broke down users to 3 different user groups to get a more accurate estimate  
  • Assumptions: You did a great job describing your assumptions and why they were reasonable assumptions

Areas of Improvement 

  • I think you decided to focus on cost of photos taken by phone which is fine. I would have just clearly stated it in the beginning as my assumption since there are other types of photos such as photos uploaded via desktop 
  • Provide your formula first: I would have mentioned the impact of data centers in the beginning   
  • Lifecycle of a photo: I think it's fair to assume photos are stored for longer than year. What should that number be in your opinion?  
  • I would also consider a less than 100% penetration rate on Android users since some people don't have Google Photos on the cloud
  • Consider compression: Google most likely compresses their files prior to storage. It's a good idea to either mention that you're assuming no compression or consider a 80% reduction on file storage due to compression  
  • Sanity check: Do a quick sanity check to ensure that your numbers make sense and you’re not off by an order of magnitude 

Hope it helps. 

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  • US only
  • Storage cost onll
 

Calculation= Total photo uploaded * average size * cost of string average photo (/year)

 US population 300M. Breakdown

  • 0-20= 75M=>10 and above=>75M/2
  • 20-40=75M
  • 40-60=75M
  • 60-80=75M=>below 70=>75M/2

 Total =220M 

 Assumption -> all these people have capability to upload photo by laptop or phone. they have internet or data coverage

 Not all of these people will upload photo. May prefer to use their laptop disk/hard disk stoareg to store photos-> 10% are like that

220*90%=>198M~200M

Possible Market segmnet= 200M has the possibility of uploading photo to to cloud storage.

People mostly use phone to take picture. Assumption people with android phone people will use Google product-> google photo.

Moreover, people who don’t have smart phone will probably never have apple laptop (costly). They will have cheap windows laptops and use google to upload the photos as its free.

80% market share is android- so assuming 80% of these people whether using phone or laptop will use google photos

So, possible people segment=160M.

Out of 160M not everybody will upload equally

  • 15-30 – young group= say 10 photos weekend + 20 photos during week= 30 photos per week.
  • 30-45 – families with young kids=10 photos weekend + 10 photos during week=20 photos.
  • 45-65= 5 photos per week.

 Let’s say 160M is equally distributed among above groups. So, around 53M each group

 

 Total photo per weeks = 53*30+53*20+53*5=1590+1060+159=2809~3000M=3B

 Different photos have different size based on camera used. For simplicity I will take on average its 2MB

 Then per weeks storage size =3B*2MB=6Petabyte

 Per year=(6*52week)=312Ppetabyte= 312*10^6 GB

Unit cost of storing = 0.002/GB

Total Cost of string = (0.002/GB)*312*10^6=624*10^4=624*10^3=624,000

 

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Clarification questions:

Is the cost required to be calculated for per person or total cost ? (Total cost annually for Google)

Is this only for phone users using the photos app or storing photos on google cloud? (just phone users using photos app).

 

Equation:

To estimate the cost, we need to know the no. of users * avg photos usage of the user (photos storing habit)*size of an average photo*price per photo storage.

 

No. of users of Google photo app. (comes from mainly android phone users, as default application).

Total no. of population worldwide =7B of which android has 35% marketshare worldwide~ 2.4B.

Assuming atleast 80% of those users use google photo app ~1.9B users.

 

Different kind of users type of photo app-

User Type

% of Users

No. of users

No. of photo clicked/user

Total no. of photos in a year

High users

20%

380M

1000/year

380B photos

Medium users

60%

1.2B

500/year

600B photos

Low users

20%

380M

100/year

380B photos

 

i.e A total of ~1100B photos a year. Assuming a size of 2MB on an avg, the total size of photos= 2200B MB (i.e1T MB)

Assuming the price of storage is $2 for 100 GB (i.e: 100*1000MB), the price for 2200B MB is $44M

 

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  1. Clarifying questions:

 

  • How does Google Photo work? What is the difference between Google Photo and Google Drive? 

=> Google Photo is the free application for storing photos and videos with limited size.

=> Google Drive is limited within 15GB for free. You have to pay if you want to use more and the size of files in Google Drive is unlimited.

  • Which period of time do you want me to estimate? Cost per month or per year?

=> Annually

  • Cost for storing in Google Photo? Not closure

=> I know that the price in Google Drive is $2/100 GB/month

=> I assume that the cost of Cloud takes ~10% of revenue => $0.02/GB/year

 

  1. Estimation

 

  • Result = Number of users x Storage per users x Cost

 

  • Number of users: 

    • World population ~8 billion => 50% people storing photo => 4 billion

    • 40% of people store offline using hardware, …

    • 60% of people store online => 4x60% = 2.4 billion people

    • Market share of photo/videos online storage

      • Google Photo: 20% => 2.4x20% = 480 million people

      • Google Drive: 10%

      • Dropbox: 20%

      • One Drive: 15%

      • Flickr: 15%

      • Others: 20%

 

  • Storage per user:

    • Photo:

      • ~12 albums/year

      • ~1000 photo/albums

      • 0.5Mb-4Mb/photo in Google Photo => 2MB/photo

=> 12x1000x2MB = 48 GB/user/year

    • Video:

      • 10 times per year

      • Original size of videos per year = maximum of typical SD card (16-64Gb => ~32Gb)

      • Compression rate: 10%

=> 10x32x0.1 = 32 GB/user/year 

Storage/user/year = 32 + 48 = 80 Gb/year

 

Cost of storing google photos on the photos app = 480 mil x 80 x $0.02 = $768 million

 
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