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What is locality-aware load balancing, and why does it help latency and cost?
Istio & Service Mesh · Intermediate level
Answer
Locality-aware load balancing prefers endpoints in the same zone, region, or network locality when possible. It helps reduce latency, cross-zone or cross-region cost, and blast radius during partial failures.
Technical explanation
Kubernetes and cloud environments often label nodes with topology information such as region and zone.
Istio can use locality information and failover rules to prefer local endpoints and fail over only when needed.
This is especially valuable for multi-zone and multi-cluster services where cross-zone traffic has both performance and cost impact.
Hands-on example
Example design:
Service checkout runs in zones a, b, and c.
Clients in zone a prefer checkout pods in zone a.
If zone a endpoints become unhealthy, traffic fails over to b or c.
Measure cross-zone bytes before and after to prove latency and cost improvement.
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