Nginx vs HAProxy

Nginx and HAProxy are both high-performance reverse proxies used extensively in production architectures, but they have different strengths. Nginx doubles as a web server and caching proxy. HAProxy is a purpose-built load balancer with superior health checking and L4 capabilities.

Architecture and Design Philosophy

Nginx — The Swiss Army Knife

Nginx started as a web server designed to handle the C10K problem. It uses an event-driven, non-blocking architecture that efficiently handles thousands of concurrent connections. Over time, it evolved into a reverse proxy, load balancer, HTTP cache, and even a mail proxy.

HAProxy — The Load Balancing Specialist

HAProxy was built from the ground up as a load balancer and proxy. It does one thing exceptionally well: routing traffic to backend servers with maximum reliability and performance. It does not serve static files or cache content.

Load Balancing Features

HAProxy has more sophisticated load balancing out of the box: advanced health checks (HTTP, TCP, script-based), connection draining, stick tables for session persistence, and rich ACL rules for traffic routing. Many of these features require Nginx Plus (commercial) in the Nginx ecosystem.

Nginx's open-source load balancing is capable but basic: round-robin, least-connections, and IP hash. Active health checks, session persistence, and advanced monitoring require the commercial Nginx Plus subscription.

Common Production Pattern

Many architectures use both: Nginx at the edge for SSL termination, static content serving, and caching, with HAProxy behind it for sophisticated backend load balancing and health checking. This combines the strengths of each.

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