System requirements

Functional:

1. We want URL to be in between 5-10 character as it strikes balance
2. We will have alphanumeric characters in URL, with special characters supported.
3. System needs to support deletion and update of the URLs

Non-Functional:

• System should be resilient
• it should optimize space

Capacity estimation

1 million active users

1 million * 5 URLs per month = 5 million URLs per month

5 million * 200 bytes = 1 GB storage per month

Peak QPS = 280

API design

POST api/v1/shorten-url

Body - Long URL

GET api/v1/short-url

Database design

id

long URL

short URL

other metadata

High-level design

so we will have

1) Load balancer

2) Servers, responsible for generating short URL as well as supporting redirect for input short URL

3) Database

Request flows

1) Client will send request with long URL,

we will check if it already exits in DB,

if yes then we will return short URL,

if no then we will generate short URL and return short URL

2) If user provide short url then we will try to find the corresponding long URL and we will redirect request to the URL,

In terms of response code , we could return 302 or 302,

both has it;s own advantage and disdvantages

Detailed component design

Lets deep dive into generation of short URL

We have 2 options

1) as we technically have 62 letters to choose from we can have URL that is let's say 7 letters this will give us 62^7 URLs

we can use hash function and get the first 7 characters and check if it exists in the DB or not, if it is then we append random character to get new string, this type of short URL doesn't increase in time.

the other option is

generate unique number for each URL we can use time based unique number generator and then use base 62 conversation,

e.g 11057 will be converted to 2TX as short URL

How will deletion or updation will work

1) For deletion we will simply remove that URL for the storage

2) For the updation we will need to depete and follow the same procedure of generating new URLs

Trade offs/Tech choices

Mechanism to choose for short URL,

1) Hash based

2) or unique number based,

Hash based url are not predictable vs other one is predictable so based on security needs we can choose the one that fits us

regardng returning 302 vs 301 for redirectm 301 is permenent redirect vs 301 is temporary redirect, choosing 301 will avoid muliple calls but it lacks the capability to get the right tracking

Failure scenarios/bottlenecks

1) If URL is not found we will return 400

2) THe unique number generation could become bottleneack, we are going to use the distributed time based generation.

3) Database could be the vbottleneack, we can use distribute3d key value based storage

Future improvements

1) MOnitoring

2) alerting