Network Inter Zone Egress
Traffic between zones inside the same region. The per-gigabyte rate is low enough to look negligible and high enough to matter at volume, which is why it tends to show up as an unexplained line rather than as something anyone chose.
Billed: Per gibibyte crossing zones within one region. Small per gigabyte, very large in aggregate for chatty systems.
What triggers this charge
- A Kubernetes service routing to pods spread across zones — the default behaviour for a regional cluster, on every internal call.
- Distributed databases (Cassandra, Kafka, Elasticsearch) replicating across zones for availability. This is continuous and proportional to write volume.
- A regional load balancer sending traffic to a backend in another zone.
- Chatty microservices where one user request fans out into dozens of internal calls, each of which may cross a zone.
How to reduce it
Use topology-aware routing in Kubernetes
Topology-aware hints keep service traffic within a zone when a healthy endpoint exists there. It is a configuration change, not an architectural one, and it typically removes most of this charge.
Weigh the availability requirement honestly
Multi-zone replication buys zone-failure survival. For a non-critical workload, single-zone with good backups may be the right trade — but make it a decision rather than a default.
Reduce the fan-out
Batching internal calls and caching hot lookups cuts inter-zone volume proportionally, and usually improves latency at the same time.
Rates
Related charges
Now find out how much of this you are actually paying.
Finitizer breaks your Google Cloud bill down to the SKU, shows how each one has moved since last week, and separates rate changes from usage changes — so you know whether to talk to engineering or to procurement.