HAProxy: The Reference Architecture for High-Performance Load Balancing & Traffic Control

TL;DR

The load balancer is the front door to your infrastructure. Relying on standard cloud services like the AWS Application Load Balancer (ALB) often means paying a “convenience tax.” The billing model is opaque (LCUs), and technical flexibility ends where the cloud GUI stops. HAProxy, the global standard for high-load systems, gives you back control. It offers unmatched performance, granular traffic control, and deterministic costs—as a transparent ingress controller directly in your Kubernetes cluster.

1. The Architectural Principle: Event-Driven Engine Instead of Blackbox

An AWS ALB is a “blackbox.” You don’t know how many instances are running, and you have no influence over caching or TCP optimization. You configure rules and hope AWS scales.

HAProxy is based on an event-driven architecture. It is optimized to handle tens of thousands of connections with minimal CPU and memory overhead.

• Full Stack Control: You have access to every parameter of the TCP/HTTP stack. Timeouts, buffer sizes, and keep-alive behavior can be tuned down to the millisecond.
• No “Warm-Up”: While an ALB often takes time to scale in the background during sudden load spikes (or throws 502 errors), HAProxy can handle traffic explosions immediately, as long as the underlying hardware has resources.

2. Core Feature: Advanced Routing & ACLs

Cloud load balancers quickly reach their limits with complex logic. An ALB allows only a limited number of rules and simple path forwarding.

HAProxy offers a powerful configuration language based on ACLs (Access Control Lists).

• Granularity: You can make decisions based on anything: source IP, user agent, cookies, SSL version, custom headers, or even payload contents.
• Lua Scripting: If the standard configuration isn’t enough, you can integrate Lua scripts. This enables complex logic like “If the user is from country X and header Y is set, route them to service Z and set cookie A, but only 50% of the time.”

3. Shield and Rate Limiting

Security starts at the edge. HAProxy acts as an extremely efficient shield in front of your applications.

• Rate Limiting: You can set aggressive limits (e.g., “Maximum 10 login attempts per minute per IP”), enforced in the load balancer’s memory before the request even reaches your application. This protects against brute-force and DDoS attacks.
• Global Profiling: HAProxy maintains stick tables to track client behavior over time, going far beyond simple firewalls.

4. Operational Models Compared: AWS ALB vs. ayedo Managed HAProxy

This is where it is decided whether your costs explode with traffic and how flexibly you can respond to requirements.

Scenario A: AWS ALB (The LCU Cost Trap)

The Application Load Balancer (ALB) is the standard, but the pricing model is tricky.

• Opaque Costs: You pay not only per hour but also per LCU (Load Balancer Capacity Unit). This formula is extremely complex (based on new connections, active connections, bandwidth, and rule evaluations). A DDoS attack or inefficient client behavior can multiply your bill unnoticed.
• Technical Limits: ALBs have hard limits (e.g., timeout limits for WebSockets, header size limitations). If your application requires long connections, AWS terminates them mercilessly.
• Lack of Transparency: If requests are slow, it’s hard to say: Is it AWS or the app? Metrics are aggregated and often not detailed enough.

Scenario B: HAProxy Ingress with Managed Kubernetes by ayedo

In the ayedo app catalog, HAProxy runs as a Kubernetes ingress controller.

• Flat-Rate Performance: The load balancer runs on the worker nodes (or dedicated ingress nodes). You pay for CPU and RAM. Whether 10 or 10,000 requests per second—there are no hidden “transaction fees.”
• Portability: Your routing rules (Ingress or Gateway API definitions) are portable Kubernetes objects. They work identically on AWS, Azure, or on-prem.
• Observability: HAProxy provides extremely detailed Prometheus metrics on every single backend server, retries, and response times. You can see exactly where the bottleneck is.

Technical Comparison of Operational Models

FAQ: HAProxy & Ingress Strategy

Does HAProxy completely replace the AWS Load Balancer?

Most often, a classic Network Load Balancer (NLB) from AWS is used to direct traffic to the Kubernetes nodes (Layer 4). But all Layer 7 logic (SSL termination, path routing, header manipulation) is handled by HAProxy. This saves massive costs, as NLBs are much cheaper and simpler than ALBs.

Isn’t HAProxy too complex to configure?

The raw haproxy.cfg can be intimidating. In the ayedo stack, however, we use the HAProxy Ingress Controller. You configure it via standard Kubernetes Ingress Resources (YAML). The complex config is generated automatically. For special cases, you use simple annotations in the YAML.

Does HAProxy support modern protocols like gRPC?

Yes, excellently. HAProxy was one of the pioneers in supporting HTTP/2 and gRPC. It can load balance, inspect, and route gRPC calls. This is often a weak point of simpler load balancers.

What about WAF (Web Application Firewall)?

HAProxy has basic WAF functions (SQLi/XSS filters) onboard. For deeper protection, it can be extended with ModSecurity or Coraza (Wasm). Unlike AWS WAF, you don’t pay per request or per rule but have the full computing power of your nodes available.

Conclusion

Performance is a feature, and latency is the enemy. AWS ALBs are convenient, but they mask inefficiencies and tie your costs linearly to your success (traffic). HAProxy breaks this logic. It is the “Formula 1” of load balancers—built for speed, transparency, and absolute control. With the ayedo Managed Stack, you get this power as an easily consumable ingress controller that makes your applications faster and cleans up your cloud bill.