Building a URL Shortener: My First Real Dive into Backend Fundamentals
I recently built a URL shortener, and it turned out to be one of the best decisions I've made since I started learning backend development. It was actually recommended to me as a starter project, and I can see why. It's small enough to finish in a reasonable amount of time, but it touches almost every core backend concept: databases, caching, rate limiting, and HTTP semantics you don't really…
Building a URL Shortener: My First Real Dive into Backend Fundamentals
I recently built a URL shortener and found it to be one of the best decisions I've made since starting to learn backend development. It was recommended as a starter project, and I can see why. This project covers nearly every core backend concept, including databases, caching, rate limiting, and HTTP semantics that you rarely think about in the frontend.
A URL shortener is quite simple - it takes a long URL, generates a short, unique code (usually 8-11 characters) for it, and stores the pair together. When someone visits the short link, the service looks up the code and forwards them to the original URL. A good example is LinkedIn's custom URLs, which are human-friendly aliases for longer, uglier URLs.
To generate the short code, I used the nanoid library. I wrapped the save operation in a retry loop since collisions are possible, even though they're unlikely. This was my first hands-on experience working with a relational database like PostgreSQL, not just reading about it. The Location header was the most eye-opening part of the project for me.
Up until now, I had only used it in the frontend but never understood its true purpose. I now view it as the API's way of guiding you to the correct destination. The Location header is the API's way of pointing you somewhere else. When you call an endpoint (e.g., /abc123), instead of sending back the destination content itself, it responds with a redirect status code and a Location header that tells your browser to go to the specified URL. No extra JavaScript or manual navigation is required.
I also decided to incorporate Redis into the project as a rate limiter. This was an excuse to use Redis, which I've heard a lot about. Redis is perfect for rate limiting because it provides fast, in-memory counters. I created a helper function to wrap the connection logic, making it easy to use Redis throughout the app. The rate limiting middleware sits in front of the alias routes and keys each counter by IP address.
It increments the counter on every request and sets an expiry for the window, resetting it the first time it sees the key.
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