Calculate composite SLA for multi-service GCP architectures.
Last verified: May 2026
Add GCP services in your architecture as serial dependencies. Enable redundancy per service to model parallel availability.
Output will appear here...The GCP SLA Calculator computes composite SLA percentages for multi-service Google Cloud architectures. When your application depends on multiple GCP services chained together, the effective uptime guarantee is the product of each service's individual SLA. This tool lets you select services, specify redundancy configurations (single region, multi-region, zonal), and instantly see the composite SLA along with expected monthly and yearly downtime. It helps architects make informed decisions about redundancy trade-offs.
Your team is proposing a new architecture: Cloud Run (99.95%) → Cloud SQL HA (99.95%) → Cloud Storage (99.9% for regional). Composite serial SLA = 99.8%, or ~88 minutes/month of expected downtime. The architect wants to claim '99.99% uptime' to leadership. The calculator shows this is mathematically impossible with the chosen services without redundancy. Adding multi-region Cloud SQL via cross-region replicas + multi-region GCS bucket pushes composite to 99.99%+, justifying the 2x infrastructure cost vs. the original plan.
The composite SLA math is multiplicative for serial dependencies: chain a 99.9% Cloud Run service to a 99.95% Cloud SQL = 99.85% composite, which is 65 minutes/month of expected downtime instead of 22 minutes. The naive 'we use 99.95% services so we have 99.95% uptime' assumption is the most common availability estimation mistake.
Multi-region GCP deployments dramatically improve composite SLA: 99.95% × (1 - (1-0.9995)^2) = 99.999975% effective. The math justifies the multi-region cost for any workload where downtime cost exceeds 2x the multi-region price premium.
GCP's published SLAs are availability-only, NOT durability or performance. A service can be 'available' (returning successful API responses) while suffering 5x latency or returning incorrect data. Contractual SLA credits don't apply to performance degradation. Design monitoring around YOUR actual SLO, not just the provider's advertised SLA.
The calculator computes composite SLA for serial chains as the product of individual SLAs (99.9% × 99.95% = 99.85%). For redundant configurations (parallel services where any healthy instance keeps the system up), it computes 1 - (1-individual)^N where N is the number of redundant instances. Output includes the resulting composite percentage plus expected monthly and yearly downtime in minutes/hours.
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