Please note the following numbers are for this exercise only as they are not real numbers from Twitter.

Assumptions:

300 million monthly active users.

50% of users use Twitter daily.

Users post 2 tweets per day on average.

10% of tweets contain media.

Data is stored for 5 years.

Estimations:

Query per second (QPS) estimate:

Daily active users (DAU) = 300 million * 50% = 150 million

Tweets QPS = 150 million * 2 tweets / 24 hour / 3600 seconds = ~3500

Peek QPS = 2 * QPS = ~7000

We will only estimate media storage here.

Average tweet size:

tweet_id 64 bytes

text 140 bytes

media 1 MB

Media storage: 150 million * 2 * 10% * 1 MB = 30 TB per day

5-year media storage: 30 TB * 365 * 5 = ~55 PB