https://www.youtube.com/watch?v=Cg3XIqs_-4c

Problem Statement: Given a long URL, we have to create a short URL. Given a short URL, we have to redirect the user to the long URL. Has to be low latency and have high availability.

Areas to cover:

API Design

• POST /create-url
• GET /{short-url}

Questions to ask:

• How long should the URL be?
• How much should be service scale?
  • Example math: 1k URLs * 60 seconds * 60 minutes * 24 hours * 365 days = 31.5B URLs created every year
  • Can estimate 10x read volume vs write volume
  • This means ~300B reads per year
• What characters can be used?
  • a-z
  • A-Z
  • 0-9

Design:

Simple - User → Load Balancer → Web Servers → DB

First thing to try: Add a cache to the web servers

Next thing to try: Scale up web servers and cache cluster

Next: Eliminate cache, replace with zookeeper