Design a TinyUrl-like Service

Table of Contents

1. Introduction
2. What is a URL Shortener?
3. Key Things to Know
   1. Base64 Encoding
   2. Key Generator Engine
   3. Reduced Cache
   4. Load Balancers
   5. MySQL Database
4. What Not to Answer in the Interview
5. Use Cases
   1. Unique ID Generation Logic
   2. Create Short URL
6. Unique ID Generation
7. Architecture Design
8. Create Account Service
9. Create Short URL Service
10. Get Long URL Service
11. Lookup and Sharding
12. Conclusion
13. FAQs

Article

Introduction

Welcome to this article where we will deep dive into the system design of a URL shortener. We will explore the key components involved in building a URL shortener system and discuss its various use cases and advantages.

What is a URL Shortener?

A URL shortener is a simple tool that takes a long URL and converts it into a shorter URL. It is commonly used in situations where long URLs need to be shared, such as on social media, print materials, or promotional items like cards and t-shirts. It provides a convenient and user-friendly way to condense the length of URLs without sacrificing functionality.

Key Things to Know

Before we delve into the details of URL shortener system design, let's first understand some key concepts that play a crucial role in its functioning.

Base64 Encoding

Base64 is a character encoding scheme that uses a set of 64 characters, including uppercase and lowercase letters (A-Z, a-z), numbers (0-9), and two special characters. This combination of characters allows for the creation of unique keys. In the context of a URL shortener, base64 encoding is used to generate the unique IDs that make up the shortened URLs.

Key Generator Engine

The key generator engine is an essential component of a URL shortener system. It is responsible for generating the unique IDs using the base64 characters. This engine typically operates as a separate application that builds the unique characters needed for the short URLs.

Reduced Cache

A reduced cache is an in-memory database that stores key-value pairs. In the context of a URL shortener, it allows for efficient retrieval of the corresponding long URL by using the unique key associated with the short URL. This cache helps improve the performance of the system by reducing the need to query the database repeatedly.

Load Balancers

Load balancers play a crucial role in scaling the URL shortener system. When the system receives a large number of requests, a single server may not be able to handle the load efficiently. In such cases, load balancers are used to distribute the traffic across multiple servers to ensure balanced resource utilization and improved performance.

MySQL Database

The MySQL database is used to store the mapping between the short URLs and their corresponding long URLs. It acts as a persistent storage solution for the system, allowing for the retrieval and storage of records efficiently.

What Not to Answer in the Interview

When asked about how to design a URL shortener system in an interview, it is crucial to provide a scalable and efficient solution. Many candidates often make the mistake of presenting a solution that may work technically but fails to scale efficiently. One common approach is to depict a diagram with laptops, computers, CDNs, and Java hash tables. While this may seem reasonable, it lacks scalability in practice. It is vital to present a diagram or solution that showcases a scalable system design.

Use Cases

In the following sections, we will explore two important use cases of a URL shortener system: unique ID generation logic and creating short URLs.

Unique ID Generation Logic

Have you ever wondered how platforms like YouTube generate unique IDs for each video? They utilize base64 encoding to create a set of unique characters. By using a combination of characters like uppercase and lowercase letters and numbers, a substantial number of unique IDs can be generated. For example, with just 11 characters, YouTube can create over 73 quadrillion unique IDs. This ensures that they will not run out of numbers for a very long time. Similarly, a URL shortener system needs to generate unique IDs for its short URLs.

Create Short URL

The "create short URL" service is responsible for generating a short URL from a given long URL. When a request is made to create a short URL, the system generates a unique key using the key generator engine. It combines this key with a short domain name, such as bitly.com, and creates the short URL. The mapping between the generated key, short URL, and the corresponding long URL is stored in a table, making it easy to retrieve the long URL when needed.

Unique ID Generation

To create a URL shortener system, we need to generate unique IDs for the short URLs. Typically, a system can use either 7 or 8 characters for its short URLs, excluding any special characters. By utilizing a set of 62 characters (26 uppercase letters, 26 lowercase letters, and 10 numbers), a vast number of unique IDs can be generated.

Architecture Design

The architecture of a URL shortener system involves various components working together to ensure its smooth operation. At a high level, the system consists of phones or laptops connecting to a Content Delivery Network (CDN), which, in turn, connects to load balancers. The system has three essential services: create short URL, get long URL, and create account. These services can be deployed in EC2 instances or Docker containers to achieve scalability and flexibility. The system also includes a reduced cache, key generator engine, and MySQL database for efficient storage and retrieval of data.

Create Account Service

The create account service allows users to create an account by providing their personal and company information. This information is stored in a user table, making it easily accessible whenever user details need to be retrieved.

Create Short URL Service

The create short URL service is responsible for generating a short URL from a given long URL. It utilizes the key generator engine to create a unique key, which is combined with a short domain name to form the short URL. The mapping between the key, short URL, and long URL is stored in a table for future reference.

Get Long URL Service

The get long URL service allows users to retrieve the original long URL by providing the short URL. When this service receives a request, it first checks the reduced cache to see if the long URL exists. If it is not found in the cache, the service queries the database to retrieve the long URL. Subsequently, the retrieved long URL is returned to the user, and the service stores it in the cache for future use.

Lookup and Sharding

To optimize the URL shortener system, a lookup mechanism is implemented. This lookup functionality helps determine which database stores the data based on the provided long URL or expiration date. By sharding the database based on expiration dates, efficient retrieval of data becomes possible, resulting in better overall system performance.

Conclusion

In conclusion, building a URL shortener system involves several key components and considerations. By understanding concepts like base64 encoding, key generation, caching, load balancing, and database usage, it becomes possible to design a scalable and efficient solution. The architecture of such a system involves various services working together to provide short URLs and retrieve the original long URLs when needed. With proper implementation and optimization, a URL shortener can be a valuable tool in simplifying and sharing lengthy URLs.

FAQs

Q: How does base64 encoding work? A: Base64 encoding is a character encoding scheme that represents binary data as a string of 64 characters. It accomplishes this by converting the binary data into a series of 6-bit chunks and mapping them to specific characters from a set that includes uppercase and lowercase letters and numbers.

Q: Can a URL shortener system handle a large number of requests? A: Yes, a URL shortener system can handle a large number of requests by leveraging load balancers to distribute the traffic across multiple servers. This ensures that no single server becomes overwhelmed and allows for better scalability and improved performance.

Q: How are unique IDs generated in a URL shortener system? A: Unique IDs in a URL shortener system are typically generated using base64 encoding. By combining a set of characters, such as uppercase and lowercase letters and numbers, a large number of unique IDs can be generated. The length of the generated ID depends on the desired number of unique combinations.

Q: How does caching improve the performance of a URL shortener system? A: Caching in a URL shortener system involves using an in-memory database, such as a reduced cache, to store frequently accessed data. By storing the mapping between short URLs and long URLs in the cache, the system can retrieve the information faster, eliminating the need for repetitive database queries.

Q: How can a URL shortener system ensure scalability? A: A URL shortener system can ensure scalability by utilizing load balancers to distribute the incoming traffic across multiple servers. This allows the system to handle a larger number of requests without overwhelming a single server. Additionally, methods such as database sharding can be implemented to distribute the data across multiple databases for efficient storage and retrieval.