Article related to Capacity Calculations
How I Calculate Capacity for Systems Design - 2

Instagram Calculations

1. Daily Active Users (DAU) and Posts

Total users: 600 million
Daily Active Users (DAU): 200 million
Assume Percentage of DAU posting 2 posts each day: 25%

Write Request

Total posts per day= 200 million x 25% x 2 = 100 million posts/day - 100M posts/day

Total posts per second = 100 million posts/seconds in a day
= 100M/100K = 1000 / seconds

Read Request

Views per day:

Total views per day = 200 million x 100 reads = 20 billion
views/day

Total views per seconds = 20 billion views / seconds in a day = 200K/seconds

Overall Traffic Estimations:

Write per second: 1000/seconds
Read per second: 200K/seconds

2. Storage Calculation for One Day

let's stick to the above calculation where 100M write requests we have.

Breaking them into Image Post & Reel Post only for now.

Here, you can also consider another post request like like, comment, share etc..

Images

Percentage of posts that are images: 70% of 100M

So,

Number of image posts per day:

Image posts per day = 70% times 100 million = 70 million

Storage per image: 200 KB
Total storage for images:

Storage for images = 70 million x 200 KB = 14,000,000,000 KB = 14,000 TB

Reels

Percentage of posts that are reels: 30% so,
Number of reel posts per day:

Reel posts per day = 30% times 100 million = 30 million

Storage per reel: 2 MB
Total storage for reels:

Storage for reels = 30 million x 2 MB = 60,000,000 MB = 60,000 TB

Total Storage Needed for One Day

Total storage:

Total storage = Storage for images + Storage for reels

Total storage = 14,000 TB (images) + 60,000 TB (reels) = 74,000 TB = 74 petabytes (PB)

3. Storage Calculation for Five Years

Assuming 365 days per year:
Storage needed for one day: 74 PB
Storage needed for five years:

Total storage for five years = 74 PB times 365 days times 5 years

Total storage for five years = 135,350 PB = 135.35 ~ 130 exabytes (EB)

4. Bandwidth Calculation

1. Incoming Data Bandwidth

Total data coming to the server per day: 74 PB
Convert to Mbps:

74 PB = 74 x 1000 x 1000 x 1000 MB

Data per day = 74,000,000,000 MB

Data per second = 74,000,000,000 MB / 86400 seconds ~ 856,481.48 MBps ~ 836.67 GBps ~ 800 GB/sec

2. Outgoing Data Bandwidth

Views per day: 20 billion

Assuming 50% for images and 50% for reels:

Image Posts Assumption

Each image post: 200 KB
Total outgoing data for images:

20 billion × 0.5 × 200 KB = 2,000,000,000,000 KB = 2,000,000,000 MB = 2,000 TB

Reels View Assumption

Each reel post: 2 MB
The user watches 1 out of 5 reels:

20 billion × 0.5 × 1/5 × 2 MB = 4,000,000,000 MB = 4,000 TB

Total Outgoing Data

2,000 TB (image posts) + 4,000 TB (reels) = 6,000 TB

Convert to GBps:

6,000 TB = 6,000,000 GB

Data per second = 6,000,000 GB / 86,400 seconds ≈ 69.44 GBps ~ 70GBps

Summary

Daily Storage Requirement: 74 PB
Five-Year Storage Requirement: 135 EB
Incoming Bandwidth Requirement: ~856,481.48 MBps (or ~800 GBps)
Outgoing Bandwidth Requirement: ~69.44 GBps (or ~70 GBps)

Twitter Calculations

Twitter's Traffic Estimations and storage requirements:

Assumptions:

300 million monthly active users (MAU): This is the total number of unique users who use Twitter at least once a month.
50% of users use Twitter daily: This implies that half of the monthly active users are active on Twitter every day.
Users post 2 tweets per day on average.
10% of tweets contain media: Media can include images, videos, etc.
Data is stored for 5 years: This is the retention period for storing the tweets and media data.

Estimations:

Daily Active Users (DAU):

DAU = 300 million x 50% = 150 million

Tweets QPS (Queries per Second):

Total tweets per day:

Total tweets / day = 150 million users x 2 tweets per user = 300 million tweets

Tweets per second (assuming tweets are uniformly distributed throughout the day):

Tweets / second = 300 million tweets x 24 hours x 3600 seconds ~ 3472 tweets per second

approx 3500 tweets per second (rounded for simplicity)

Peak QPS: Often, systems need to handle peak loads, which can be higher than the average. Assuming the peak QPS is double the average: text Peak QPS = 2 x 3500 approx 7000 tweets per second

Media Storage Estimation:

Average tweet sizes:

tweet_id: 64 bytes
text: 140 bytes
media: 1 MB (only for tweets containing media, which is 10%)

Daily media storage:

Daily media storage = 150 million users x 2 tweets per user x 10% x 1 MB

300 million tweets x 10% x 1 MB ~
30 million tweets with media x 1 MB ~
30 TB per day ~ 30TB/Day

5-year media storage:

5-year media storage = 30 TB per day x 365 days x 5 years
30 TB/day x 1825 days

54,750 TB

Approx 55 PB (rounded for simplicity, where 1 PB = 1000 TB)

Summary:

Daily Active Users (DAU): 150 million
Tweets QPS:
- Average: ~3500 tweets per second
- Peak: ~7000 tweets per second
Media Storage:
- Daily: 30 TB
- 5-year: ~55 PB

These estimations provide an understanding of the scale at which Twitter operates in terms of query load and storage requirements.

Thanks
Zeeshan