Requirements

Functional Requirements:

• Create a short URL for a given long URL.
• Return the long URL associated with a given short URL.

Non-Functional Requirements:

• Given a long url create a short url
  • This requires very low latency
• Given a short url redirect to a long url
  • This requires very high availability

API Design

POST: /create-url

• Params: long-url
• Status Code: 201 Created

GET: /{short-url}

• Status Code: 301 Permanent Redirect

High-Level Design

How long should the url be?

What is the scale of the application?

Example 1,000 URLs generated per second

1000 * 60 (seconds in an minute) * 60(minutes in an hour) * 24(hours a day) * 365 (days in a year)

10 to 1 read to write requests means 200 billion reads per year

What characters can we use?

a -z = 26

A - Z = 26

0 - 9 = 10

Total 62 characters

How many unique short urls can be created?

1^62 = 62. (1 character)

2 ^62 = 3, 844 (2 characters)

...

6 ^ 62 = 56 billion (6 characters)

7^62 = 3.5 trillion (7 characters)

Detailed Component Design

Deep dive into 2-3 key components. Explain how they work, how they scale, discuss tradeoffs, capacity, and any relevant algorithms or data structures.