Requirements

Functional Requirements:

• Given a URL, a service should return a shortened random url resolvable by the service into the original URL
• The generated URL should have a time-to-live, after which it's deleted
• The user should be able to optinaly specify a unique url
• The service should allow anonymous URL creation

Non-Functional Requirements:

• The system should be highly available
• URL resolution should happen as fast a possible
• Links should not be guessable

Capacity Estimation

Estimate the scale of the system. Consider daily active users, read/write ratio, storage requirements, bandwidth, and any relevant QPS calculations...

Let's assume 100000 daily active users, with 10000000 overall users

One URL is maximum 128 characters long + 8 bytes per unique url (18 quintillion unique values)

We'll need at least 10000000 x 128 +8 bytes of memory ~ 1.5PB of data storage

Let's assume 100:1 read/write ratio

API Design

URL create/read/update/delete

URL analytics endpoint

Authrization

High-Level Design

• Load Balancer
• Application Server
• Database (NoSQL, no need for SQL here)

Database Design

Define the data model. Identify the main entities, their attributes, and relationships. Consider the choice of database type (SQL vs NoSQL) and justify your decision based on access patterns...

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.