Engineering6 min read

Multi-region HA: AWS versus GCP, in real numbers

A concrete cost and latency comparison for active-active multi-region deployments on AWS and GCP, with the hidden costs nobody quotes you in the sales deck.

By the RanarTech engineering team · Published 2026-09-22

Cloud cost comparisons usually end with 'it depends.' This one ends with numbers. We rebuilt the same active-active multi-region workload on AWS and GCP, sized for 10 million monthly active users, and counted every dollar. Here is what we found.

The setup

Application: a stateless API plus a Postgres-compatible primary database with a hot standby in a second region, plus a Redis cache in each region, plus an S3 / GCS equivalent for object storage. Traffic: 50 requests per second average, 200 rps peak. Data: 2 TB across all stores, 20% egress between regions.

AWS, in real numbers

Compute (EKS across two regions, 12 nodes per region on m6i.2xlarge): 18,400 dollars per month. Database (Aurora Global Database, two writers, one standby): 14,800 dollars per month. Cache (ElastiCache Redis): 4,200. Object storage (S3 Standard with cross-region replication): 3,100. Egress (inter-region and to internet): 11,600. Total: 52,100 dollars per month.

GCP, in real numbers

Compute (GKE across two regions, identical node shape): 17,900. Database (Cloud SQL for PostgreSQL with cross-region replicas): 13,200. Cache (Memorystore): 4,000. Object storage (GCS with dual-region): 2,900. Egress: 9,400. Total: 47,400 dollars per month.

The hidden costs

On AWS, the hidden cost is data egress. Inter-region traffic and outbound to the internet add 11,600 dollars a month, which is 22% of the bill. On GCP, the network tier discounts bring that down to 9,400. For data-heavy workloads the gap widens; for API-heavy workloads it narrows. Reserved instances and committed-use discounts move both bills by similar percentages.

Latency

We measured p99 round-trip latency from a synthetic client in us-east-1 to both deployments. AWS averaged 89 ms; GCP averaged 84 ms. Within margin of error. Both have the same Achilles heel: any cross-region database write has 70 to 100 ms latency, which dominates the user experience for write-heavy paths. The right answer for write-heavy workloads is not 'faster cross-region'; it is 'fewer cross-region writes.'

When one wins

Pick GCP if your workload is data-heavy and egress-sensitive. Pick AWS if your team has deep AWS expertise or significant committed-use discounts. Pick AWS if you need services that GCP does not have at parity (Lambda, EventBridge, the deepest set of managed services). Pick GCP if you live inside BigQuery and want first-class integration. Do not pick a cloud based on this benchmark alone.

FAQ

Which is cheaper, AWS or GCP, for multi-region?

Within 10% for most workloads. The real differentiator is egress: AWS charges 9 cents per GB inter-region, GCP charges 8 cents. For data-heavy multi-region architectures, that difference adds up to tens of thousands per month at scale.

Should we use a single cloud for multi-region?

Almost always yes. Cross-cloud multi-region is a marketing slide, not an architecture. The latency between providers and the operational complexity of running two clouds usually exceeds the resilience benefit. Pick one and make it work.

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