educative.io

Yelp - Design Consideration - storage calculation

Courses
,
#1

Hi,

Can you please elaborate the calculation here?

image
image864×678 48.2 KB

Course: Grokking Modern System Design Interview for Engineers & Managers - Learn Interactively
Lesson: Design Considerations of Yelp - Grokking Modern System Design Interview for Engineers & Managers

#3

You are storing SegmentID → {List of places in that Segment}
This is done with the formula:
Total Size = Number of segments x (Segment ID size in Bytes + no. of Places per segment * Place ID in Bytes)

  • There exist 60 M miles sq radius in earth. If each segment is 10 mile Sq radius → you have 6 M segments
  • you have 500M places. Consider uniform distribution of places per segment. Then number of places per segment = 500M/6M = 83.33 Places per segment ID
  • 1 segment ID will have 83.33 places
  • Total size of one record = 8Bytes for SegmentID + 8Byte * 83.333 places = 674.67 bytes
  • For 6 M segments: 6 Million * 674.67 bytes = 4.048 GB

Note: The text incorrectly says TB but it should be GB.

#4

Hi Mansoor.

We are glad you reached out to us. The calculation performed here approximates our storage need to design Yelp.

Total_Area_of_Earth = 60M sq miles.
Search_Radius = 10 miles.
Num_of_Segments => 60/10 = 6M.

We assume 500M places (Num_of_Places) will be in the Total_Area_of_Earth.
We are assuming each Segment_ID and Place_ID to take 8 bytes.

Total_Space = (Number_of_Segments * Segment_ID_size) + (Num_of_Places * Place_ID_size) = (6M * 8) + (500M * 8)
= 48000000 + 4000000000 => 4048 MB or 4.048 GB

We are also adding these detailed calculations to the lesson in the next update.
I hope that clears up the confusion. If you have any other questions, feel free to reach out to us.

Thank you.

@micro_service_3699 Thank you for the detailed response.