High Availability Zone-aware Load Balancing

High Availability Zonal Load Balancing (HAZL) is a dynamic, request-level load balancer designed for multi-zone Kubernetes environments and available within Buoyant Enterprise for Linkerd. While it significantly reduces cloud spend by minimizing expensive cross-zone traffic, its primary objective is maintaining peak application reliability. HAZL proactively improves resilience by monitoring real-time latency and success rates for every request. If a specific zone becomes stressed or experiences increased latency, HAZL immediately redistributes traffic to healthy endpoints in additional zones to prevent failures before they occur. This intelligent routing ensures that applications remain highly available even during localized workload failures or traffic spikes. By balancing cost-efficiency with a fail-safe routing logic, HAZL ensures that zone affinity does not come at the expense of the user experience.

In this technical white paper, you'll learn how HAZL works, how it compares to Topology Aware Routing (TAR), and its advantages for reliability, cloud spend reduction, and cross-cluster communication.