Requirements

Functional Requirements:

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

Non-Functional Requirements:

• Low latency
• Reliability

API Design

POST api/v1/shorten

request body: longUrl

response: shortenUrl

GET api/v1/shorten/{shortUrl}

response: return 302 + longUrl

High-Level Design

We need an API Gateway, so it can helps us with following topics:

1. Throttling
2. Auth
3. IP whitelist

URL Redirection Service: GET API request will handled by this service, it will use read-through fetch the cache to see if the short url there, if not, it will query DB (NoSQL) and store the pair in the cache.

URL Generator Service: POST API request will handled by this service, it will generate an unique, short URL and store the in DB (NoSQL).

NoSQL: we choose to use NoSQL as we don't need ACID in this design and NoSQL is easy to do horizontal scaling.

Cache: LRU cache.

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.