API Gateway vs Load Balancer vs Reverse Proxy
In system design and distributed architectures, these three components are often confused, but they serve distinct roles — and in practice, a single production system usually uses all three together , layered on top of each other. 1️⃣ API Gateway Acts as a single entry point for client-facing APIs — crucial in a microservices architecture where dozens of services would otherwise each need their…
In system design, the terms API Gateway, Load Balancer, and Reverse Proxy are often used interchangeably, but they each have distinct purposes in a distributed architecture.
The API Gateway acts as a single entry point for client-facing APIs, especially in a microservices environment where multiple services might otherwise have separate public endpoints. It handles crucial tasks such as authentication, authorization, rate limiting, request routing, and even API composition. Other common responsibilities include request/response transformation, API versioning, request validation, quota management, and analytics/logging. Popular API Gateways include AWS API Gateway, Kong, Apigee, and Zuul.
The Load Balancer's primary role is to evenly distribute incoming traffic across multiple backend servers or instances, ensuring high availability and horizontal scalability. It prevents server overload and provides fault tolerance by detecting failed instances through health checks and routing away from them. Load Balancers operate at Layer 4 (Transport) or Layer 7 (Application) of the OSI model.
At Layer 4, they route based on IP and port numbers, while at Layer 7, they can route based on URL paths, headers, and cookies for more intelligent routing decisions. Examples of Load Balancers include AWS ELB/ALB/NLB and NGINX.
A Reverse Proxy sits in front of one or more backend servers and forwards client requests to them, hiding the backend server details from the clients. It also adds security by filtering malicious traffic and performs SSL/TLS termination, offloading the computational cost of decrypting HTTPS from backend servers. Common Reverse Proxies include Nginx, Apache HTTP Server (mod_proxy), Envoy, and Traefik.
While the same software can act as all three components depending on configuration, the distinction lies in their role and intent rather than the specific product used. An API Gateway focuses on API management (authentication, rate limiting, routing, and composition), a Load Balancer distributes traffic across servers, and a Reverse Proxy forwards requests, hides backend servers, and handles SSL/TLS termination and caching.
In a real-world architecture, clients typically interact with the system through a CDN (if present), which is followed by an API Gateway for authentication, rate limiting, routing, and API composition. The request then reaches a Load Balancer, which distributes it to the appropriate service instances. A Reverse Proxy may also be part of this stack, sitting in front of service instances to terminate SSL and perform caching.
In many deployments, the Reverse Proxy and Load Balancer may be the same component, with the Reverse Proxy described by what it does (hiding and forwarding to backends) and the Load Balancer by how it decides where to forward requests (distribution algorithm).
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
