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:

• horizontal scalability
• low latency less than 1s p99
• high availability

10k links each 2 qps

give or take 20k QPS

heavy read possibly 1000 to 1

scalable to 1 billion urls 100 million dau

storage req 1 billion * 100 byte = 100 GB

create url

POST /create

header { user auth token jwt }

req

{ originalURL: "" }

res

{ shortURLKey: "" }

retrieve

GET /

res -> redirect to the original URL

for creating new short url

client hit api gateway -> authenticate user and check rate limit to avoid ddos

once passed api gateway call shortener app

shortener app

• validate valid url
• hash the url and get the short key (eg first 6 char char 0:6)
• insert in db
• if duplicate and original url is the same return the existing short key
• if duplicate but original url is different rehash e.g char 1:7) and try reinsert
• also update cache

for retrieval

client hit api gateway

api gateway hit the retriever app

each app instance lookup cache if key exists if yes return directly

else hit the db query by the key

for scalability

each app is horizontally scalable

cache -> e.g. redis cluster, add more node for horizontal scalability + add read replica

for db -> add read replica if needed (if sql relational) else if use nosql eg. dynamo db can increase read capacity unit

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.