ALB Cross-Zone Load Balancing Cost
Cross-zone traffic is charged per gigabyte in both directions, so a balancer spreading requests across zones pays a transfer charge that same-zone routing would not incur.
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AWS
Found, explained, fixed.
Findings with a dollar figure attached, idle, oversized, orphaned, unscheduled and undiscounted spend.
Detect
ZopNight checks this automatically across AWS, with read-only access to the account.
Explain
Every finding says exactly what to change: Review cross-zone load balancing on the load balancer. Where the saving can be proven it is priced; where it cannot, the finding says so.
Fix
After a guided review, where you confirm the change, ZopNight applies a lifecycle policy, then checks the change took.
- Applies to
- Load Balancers on AWS
- The fix, by hand
- Load Balancing → the resource → check Target groups → confirm targets are evenly distributed across AZs.
- CloudWatch → AWS/NetworkELB or AWS/ApplicationELB → ProcessedBytes per AZ. If traffic is already balanced upstream, cross-zone load balancing is double-paying.
- NLB: Edit attributes → Cross-zone load balancing → Off (NLB charges per-GB for cross-zone traffic; ALB does not).
- ALB: cross-zone is on-by-default and free at the LB layer but still incurs intra-AZ vs cross-AZ EC2 data-transfer cost downstream. Leave on unless you've sharded backends per-AZ.
- Watch target health distribution + p95 latency for 24h post-change.
ZopNight does this for you after a guided review.
- Category
- Rightsizing. Resources sized for headroom they never use. A smaller size runs the same workload for less.
- Where it appears
- The Savings tab of Recommendations, with every affected resource listed.
- Rule ID
RC-1509- Full reference
Related checks
See the oversized resources in your account.
Connect a read-only role and the first pass runs on your own estate. This check, and the rest of the catalogue, with it.
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- $30M+annualised cloud spend under management
- 550K+resources tracked since launch
- 20-60%off the bill in the first month
- SOC 2Type II report, plus ISO 27001
Figures published on zop.dev.