System requirements

Functional:

1. User should be able to generate short URL from long URL
2. User should be able to get long URL from short URL

Non-Functional:

1. System should be scalable
2. System should be available
3. System can be eventually consistent
4. System should be partition tolerant

Capacity estimation

lets say we have 1M daily active users(DAU)

1. Each user creates a new short URL daily
2. Each user retrieves long URL from short URL 100 time per day

DB size Estimations :

Things to store in DB

Short URL = 8 Bytes

Long URL = 100 Bytes

CreatedDate

UserID = 50 Bytes

ID

Lets say each entry is taking around 1KB in DB

1M*1KB=10^9Bytes=1GB per day space

In 3 Years -> 1000 GB = 1TB

In 30 Years -> 10 TB

QPS :

Read QPS : 1M*100/10^5=1000 TPS

Write QPS : 1M/10^5 = 10 TPS

Cache Estimations :

We can keep cache for 24 hours : 1GB

API design

/short-url

Type : POST

Input params : long url, userId

Header : authorization

/retrieve-url

Type : GET

Input Params : short url, userId

Header : authorization

Database design

user

• userId (primary key)
• user_name
• email
• phone

url_mapping

• userId
• short_url(primary key)
• long_url
• created_date

flowchart TD

    B[client] --> C{Load Balancer}

    C --> D[ShortURLService]

    C --> E[RetrieveURLService]

    D --> F[(Database/Master)]

    E --> G[(Database/Slave)]

    E --> H[Redis Cache]

    F<-->G

Request flows

Generate URL :

1. Request from client come to load balancer, checking domain load balancer forward request to one of nodes of ShortURL Service
2. ShortURL Service generates short URL and stores mapping of short URL and long URL in Database(master)

Retrieve URL :

1. Request from client come to load balancer, checking domain load balancer forward request to one of nodes of RetriveURL Service
2. RetriveURL Service first checks the mapping of short URL and long URL in cache, if found in cache return mapping from cache only.
3. If mapping not found in cache, check mapping of short URL and long URL in Database(slave), if found save mapping in cache and return same in API response.

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?