Learn the difference between load balancer, reverse proxy and API gateway in one article

Introduction

Do you understand the differences between components as diverse as load balancers, reverse proxies, and API gateways? Not sure which one is best for your web application? These key components play a vital role in modern web architecture, and understanding how they work is essential to building efficient, secure, and scalable web applications. In this article, we will demystify these concepts and hopefully help you make an informed decision for your next project architecture implementation.

Next, let's use an inappropriate metaphor to get a preliminary understanding of the functions of each component: Imagine a courier processing center, where the load balancer acts as a foreman, ensuring that each sorting worker has a relatively even workload to achieve the load purpose; the reverse proxy is a skilled worker who is responsible for quickly knowing different couriers are sent to different destinations and ensuring correct processing; the API gateway is the center manager, responsible for supervising and controlling all aspects of sorting. Now, let's apply this analogy to the world of web applications.

Did you know that websites like Amazon and Netflix handle billions of requests every day? With so much traffic, it's critical to distribute the load efficiently. Enter the load balancer, which optimizes performance and ensures high availability. But how is a load balancer different from a reverse proxy? When should you use each component? We'll dive into these questions and more.

Load Balancing

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Load balancing is a technology that distributes workloads (such as network traffic, data requests, computing tasks, etc.) to multiple computing resources (such as servers, virtual machines, containers, etc.) in order to optimize performance, improve reliability, and increase scalability. Load balancers are usually located in front of applications, accepting and distributing incoming requests. By using algorithms to determine the best way to distribute requests, load balancers can prevent any one resource from being overloaded or failing, causing application performance to degrade or stop responding.

Load balancing can be implemented in many ways, such as allocating requests based on polling, based on the least number of connections, based on IP hashing, etc. Load balancing can also be implemented using hardware devices or software, or a hybrid solution that combines the two. Load balancing can be implemented using a variety of solutions, the following are some common ones:

1. Hardware load balancing: Use dedicated hardware devices for load balancing, such as F5, Cisco ACE, etc.
2. Software load balancing: Use software programs to perform load balancing, such as HAProxy, Nginx, Apache, etc.
3. DNS load balancing: Load balancing is performed through DNS resolution, such as using DNS polling or weight scheduling.
4. Firewall load balancing: Use firewall devices for load balancing, such as Fortinet, Checkpoint, etc.
5. Virtual IP load balancing: Multiple physical devices are combined into a virtual device, and load balancing is performed by sharing an IP address, such as LVS, Keepalived, etc.
6. CDN load balancing: Use content distribution network (CDN) for load balancing, such as Alibaba Cloud CDN, Tencent Cloud CDN, etc.

Reverse Proxy

A proxy is a special network service. In layman's terms, a proxy is a transfer between the client and the service. We can connect between the client and the server through a proxy. A reverse proxy is a proxy for a server/website. The reverse proxy server is responsible for receiving the client's request and then transmitting it to the intranet server/website.

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If you have a back-end server with sensitive information that must remain secure, such as a database of credit card numbers, you can set up a proxy server outside the firewall as a "stand-in" for the back-end server. When an external client tries to access the back-end server, it is sent to the back-end server. The actual content is located on the back-end server, securely protected inside the firewall. The proxy server is outside the firewall and appears to the client as the back-end server providing the service.

API Gateway

The API gateway is the only entrance to a system. It is the only exit for many distributed services. It achieves physical isolation. Intranet services can only be exposed to the external network and accessed by others through the gateway. From a business perspective, when a client completes a business, it needs to call multiple microservices at the same time. From a system perspective, if any application system needs to be called by other systems, it needs to expose APIs, which represent functional points. It provides a unified access entrance for external calls. It provides identity authentication, permission management, traffic control, monitoring, cross-domain processing, etc.

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Due to the popularity of microservices, API gateways have quietly emerged. The reason for the existence of API gateways is explained. It not only provides a service facade, but also coordinates the communication between different systems and serves different client interfaces.

Comparison of load balancers, reverse proxies, and API gateways

How do load balancers differ from reverse proxies? While both components distribute requests, load balancers focus primarily on improving performance, availability, and fault tolerance by distributing traffic across multiple backend servers. Reverse proxies, on the other hand, operate at the application layer and provide additional features such as URL rewriting, content compression, and access control. So, when should you choose a load balancer or a reverse proxy? That depends on your specific requirements and whether you need advanced application-level features.

But what about API Gateways? API Gateways are best suited for microservices architectures where multiple APIs require centralized management, security, and scalability. Unlike load balancers and reverse proxies, API Gateways offer advanced features such as authentication, rate limiting, request/response transformation, and monitoring. If your application relies heavily on APIs, an API Gateway can be an invaluable addition to your architecture.

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In many cases, you'll find load balancers, reverse proxies, and API gateways working together to create efficient, secure, and scalable web applications. For example, you can use a load balancer to distribute traffic across multiple reverse proxies, thereby protecting and optimizing requests to backend services. Or, you can use an API gateway in conjunction with a load balancer to manage and scale your APIs while maintaining high availability.

Summarize

Leveraging load balancers, reverse proxies, and API gateways in your business architecture can be difficult to differentiate and choose, but with the right knowledge, you can make an informed decision and choose the perfect component for your web application.

Remember, a load balancer distributes traffic across multiple backend servers, a reverse proxy provides additional application-level functionality, and an API gateway provides centralized management and security for microservices-based applications.