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Capacity Estimation

Assume:

  1. DAU = 300 M users
  2. MAU = 1 B users

A. Throughput [requests per unit of time]​

Throughput can be further divided into write-throughput and read-throughput.

So, Let's start with what all operations user can perform:

  1. Creating Short-url from long-url [Write-Operation]
  2. Fetching Long-url from short-url [Read-Operation]

A.1: Read-Throughput​

Assume every user fetches long-url for 20 short-url per day.

Total Read operations per day = DAU * 20 = 300 M * 20 = 6 B read-request per day.

A.2 Write-Throughput​

Assume 10% of users will create a 5-short-url everyday.

Total Write operations per day = (10% of DAU) * 5 = (0.1 * 300M) * 5 = 150M write requests per day

B. Storage [Bytes per unit of time]​

Assume Average storage as = Size of Long-Url + Size of Short-Url + Metadata like timestamp = 100bytes + 30 bytes + 70 bytes = 200 bytes.

Average Mapping-Size = 200 b
Total Storage per day  = Write-throughput * Average Content-Size
                        = 150M * 200 b
                        = 30 M Kb
                        = 30 Gb per day

Storage for 10 years = 30 Gb * 365 * 10
                     = 109500 Gb
                     = 0.1095 Pb

C. Cache-Memory​

Cache Memory is generally 1% of total storage per day

Cache-Memory = 1% of daily Storage = 0.01 * 30 Gb = 3 Gb per day

D. Network Bandwidth​

D.1: Ingress Traffic​

Traffic coming into the system i.e. write traffic

Ingress = Write per second
        = (Total Writing requests per second) * (Average Entry size)
        = (150M / 24/ 60/ 60) *  (200 b)
        = (1.73 K requests/sec) * (200 b)
        = 346 Kbps

D.2: Egress Traffic​

Traffic going out of the system i.e. read traffic

Egress = read per second
        = (Total read requests per second) * (Average Entry Size)
        = (6B / 24/ 60/ 60) *  (200 b)
        = (6.44 K/sec) * (200 b)
        = 13.8 Mbps