Requirements

Functional Requirements:

• return shortened version of URL
• shortened version must redirect to the original URL

Non-Functional Requirements:

• high availability
• low redirect latency
• horizontal scalability to accommodate URLs

Capacity Estimation

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

API Design

• GET api/urls
  • req: shortened link
  • response: original link
• POST api/urls
  • req: original link
  • response: shortened link
• PUT api/urls
  • req: shortened link, new mapping/shortened link
  • response: success/fail
• DELETE api/urls
  • req: shortened link
  • response: success/fail

High-Level Design

GET flow: client > cache first (reduce db hits and latency) > then load balancer if need to go to server > designated server performs db lookup or gets code from generator > writes or reads from db > directly back to client

POST flow: client > cache > load balancer > server > db lookup to see if already exists (fail response to client if so) > code generator > server > db > server (server acting as middle man between code generator service and db) > response to client

PUT flow: client > cache > load balancer > server > attempt to update db > response to client (failed/success, etc)

DELETE flow: client > cache > load balancer > server > attempt delete from db > send response to client

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.