Hidden cost · Last verified 2026-08-25

Cross-availability-zone traffic

Packets that cross AZ boundaries are often billed even when they stay in-region.

Official pricing: Source

This item is not in the current price snapshot. No rate is shown.

Spreading tasks across Availability Zones for high availability turns otherwise free same-rack chatter into a regional data-transfer meter. AWS states that data transferred in to and out from EC2, RDS, ElastiCache, and similar instances across AZs in the same region is charged in each direction, while same-AZ traffic over private IP addresses is not. Using a public or Elastic IP for that path can bill even inside one AZ. This is a different meter from the internet ladder and from the cross-region SKU. The same-region rows in this snapshot currently store a zero placeholder, so the item stays untracked and no rate is drawn; the bound SKUs only prove that regional transfer families exist. Microservice meshes, multi-AZ databases, and load balancers with unbalanced targets are the usual generators. Pin AZ affinity for chatty pairs when you can. Google Cloud and Azure distinguish zonal versus regional traffic on their network pricing pages. Add the official lines from https://aws.amazon.com/ec2/pricing/on-demand/ and https://aws.amazon.com/blogs/architecture/overview-of-data-transfer-costs-for-common-architectures/ rather than trusting an internet-egress calculator for east-west bytes.