URL Shortener

A small URL shortener built with FastAPI, PostgreSQL, Redis, and Snowflake IDs.

Quick start

1. Start Postgres and Redis:

   docker compose up -d

2. Create .env.local with the required settings:

   ENV=local
   DATABASE_URL=postgresql+asyncpg://usr:pass@localhost:5432/urlshortener
   REDIS_HOST=localhost
   REDIS_PORT=6379
   

3. Install dependencies and run:

   pip install -r requirements.txt
   python run.py

   The server runs at http://localhost:8001.

API

Create a short URL

curl -X POST http://localhost:8001/shorten \
  -H "Content-Type: application/json" \
  -d '{"url": "https://github.com"}'

Returns a short code (or the existing code if the URL was already shortened).

Resolve a short URL

GET /{code} responds with a 302 redirect to the original URL, or 404 if the code doesn't exist.

How it works

• POST /shorten generates a Snowflake ID, encodes it in base62, stores it in PostgreSQL, and caches it in Redis (1h TTL).
• GET /{code} checks Redis first, then the DB (with a Redis lock to avoid cache stampedes), then redirects.
• Rate limiting (SlowAPI, fixed-window): 5 requests/sec on GET, 1 request/sec on POST, keyed by client IP.

Stack

FastAPI · SQLAlchemy (async) · PostgreSQL · Redis · SlowAPI · Snowflake IDs