5 Equations in 5 Days: Street View Storage

This is part of a mini-series illustrating how to think about estimation prompts for Google interviews. It is also a way to build your logic instincts.

Instructions:

1. See prompt below

2. Think about how you would estimate the answer

3. Identify the variables in your thoughts

4. Derive a simple equation

What you should avoid:

1. Overthinking

2. Trying to get it perfect

Now let’s dive in:

What is the problem:

Estimate the storage space required to host all images on Google Street View?

What are the key elements:

• # images required

• avg size of images

What are the variables?

• X = # images required

• Y = size per image

  • A = Avg size of image with dense information

  • B = Avg size of with limited information

What’s the equation

=X*Y

or

= (X*A) + (X*B)

The Twists

The twists with this one are in the assumptions. How many images are needed for say an average home or stretch of highway? How dense is the information in each image? Yes, we need to break this down to at least dense cities vs rural communities, but at the heart of the question is # of images required and size of the images.

Another POV on this Prompts

Here is Stellar Peers’ answer to a similar version of the prompt. Their proposed calculation is waayyy too complex for interview day but a good way to practice.

Further Reading

Today we only care about coming up with an equation. The point of these very simple equations is to help you develop a baseline approach to the problem before worrying about the more complex assumptions. If you want more on how to come up with the numbers to put in your equation, read more here.