This tutorial shows how to build a URL shortener similar to TinyURL, covering both design and implementation.

Technologies

Golang
Gin Framework
GORM
Redis
PostgreSQL

High-Level Design

API Endpoints

API endpoints enable communication between clients and servers. We design these APIs using REST principles.

If you are new to RESTful APIs, see: restfulapi

A URL shortener mainly needs two endpoints:

URL shortening: POST request with the original long URL.
URL redirecting: GET request with the short URL.

URL Shortening

For URL shortening, we need a hash function that maps a long URL to a short URL. Conceptually, we store <shortURL, longURL> pairs.

URL Redirecting

The API supports two redirect status codes:

301 (permanent redirect): browser caches response, so future requests can bypass shortener service.
302 (temporary redirect): future requests continue passing through shortener service first.

To reduce server load, 301 is often a good default when mappings are stable.

Low-Level Design

Hash Algorithm

Like any hash strategy, collisions can happen. Checking the database on every collision is expensive.

A common approach is Base62 encoding, using characters:

0-9
a-z
A-Z

In this project, I use Twitter Snowflake to generate a unique numeric ID, then convert it with Base62.

URL Shortening Flow

Check whether longURL already exists in cache.
If not, check database, cache result, and return it.
If still not found, treat as new URL.
Generate new unique ID (Snowflake), then convert with Base62.
Store <shortURL, longURL> in database and cache, then return short URL.

URL Redirecting Flow

User requests shortURL
Load balancer routes request to web server
If short URL exists in cache, return long URL
Otherwise fetch from database
Return 301 with Location: longURL

Development

Step 1: Set Up the Project

Create a new project directory and initialize a Go module:

Step 2: Define the URL Struct

Create a URL struct for mapping shortURL and longURL:

Step 3: Implement URL Shortening

Create GenerateShortURL to:

handle POST requests
generate short URLs
return JSON response

Step 4: Implement URL Redirecting

Create RedirectShortURL to:

handle GET requests
resolve short URL
redirect to long URL

Notes:

Caching is handled in service layer logic for each function call.
Snippets above are illustrative. Full source code is available here.

Conclusion

That is all for this article.

I hope this tutorial is useful. If you need help, feel free to reach out.

Let's connect on Twitter and LinkedIn.

Thanks for reading. See you next time.

Building a URL Shortener Service using Golang