Load Balancing — Complete Gateway Traffic Distribution Guide

In this tutorial, you will learn about Load Balancing. We cover key concepts, practical examples, and best practices to help you master this topic.

Load balancing distributes client requests across multiple backend server instances. It ensures no single server is overwhelmed and provides automatic failover if a server goes down.

What You'll Learn

You'll learn load balancing algorithms, health checking, and how gateways implement traffic distribution.

Why It Matters

Without load balancing, a single server failure takes down your service. Proper load balancing ensures high availability, horizontal scaling, and consistent performance.

Real-World Use

An e-commerce platform runs 20 instances of the product service behind a gateway with round-robin load balancing. During Black Friday, they scale to 100 instances without any client configuration changes.

Implementation

# NGINX upstream configuration
upstream user_service {
    least_conn;
    server user1.example.com:3000 weight=5;
    server user2.example.com:3000 weight=3;
    server user3.example.com:3000 backup;
    keepalive 32;
}

server {
    location /api/users {
        proxy_pass http://user_service;
        proxy_next_upstream error timeout invalid_header http_500;
        proxy_next_upstream_tries 3;
        proxy_connect_timeout 5s;
    }
}

# Simple round-robin load balancer
import itertools

class RoundRobin:
    def __init__(self, servers):
        self.servers = servers
        self.pool = itertools.cycle(servers)

    def get_next(self):
        return next(self.pool)

    def remove_server(self, server):
        self.servers.remove(server)
        self.pool = itertools.cycle(self.servers)

lb = RoundRobin(["server1:3000", "server2:3000", "server3:3000"])
for _ in range(6):
    print(lb.get_next())

Common Mistakes

| Mistake | Fix | |---------|-----| | Sticky sessions without need | Stateless services scale better | | No health checks | Traffic sent to dead servers | Always configure active health checks | | Uneven load distribution | Use weighted or least_conn algorithm | | Ignoring connection limits | Set maximum connections per backend | | No circuit breaker | Failing servers degrade all traffic | Remove unhealthy servers from rotation |

What's Next

Learn about Rate Limiting at the API Gateway level.