This section of theGoogle Cloud deployment archetypes guide describes the zonal deployment archetype.

In a cloud architecture that uses the basic zonal deployment archetype, theapplication runs in a single Google Cloud zone, as shown in the followingdiagram:

To be able to recover from zone outages, you can use a dual-zone architecturewhere a passive replica of the application stack is provisioned in a second(failover) zone, as shown in the following diagram:

If an outage occurs in the primary zone, you can promote the standby databaseto be the primary (write) database and update the load balancer to send trafficto the frontend in the failover zone.

Use cases

The following are examples of use cases for which the zonal deploymentarchetype is an appropriate choice:

• Cloud development and test environments: You can use the zonaldeployment archetype to build a low-cost environment for development andtesting.
• Applications that don't need high availability: The zonal deploymentarchetype might be sufficient for applications that can tolerate downtime.
• Low-latency networking between application components: A single-zonearchitecture might be well suited for applications such as batch computingthat need low-latency and high-bandwidth network connections among thecompute nodes.
• Migration of commodity workloads: The zonal deployment archetype provides acloud migration path for commodity on-premises apps for which youhave no control over the code or that can't support architectures beyonda basic active-passive topology.
• Running license-restricted software: The zonal deployment archetype might bewell suited for license-restricted systems where running more than oneinstance at a time is either too expensive or isn't permitted.

Design considerations

When you build an architecture that's based on the zonal deployment archetype,consider the potential downtime during zone and region outages.

Zone outages

If the application runs in a single zone with no failover zone, then when a zoneoutage occurs, the application can't serve requests. To prevent this situation,you must maintain a passive replica of the infrastructure stack in another(failover) zone in the same region. If an outage occurs in the primary zone, youcan promote the database in the failover zone to be the primary database, andensure that incoming traffic is routed to the frontend in the failover zone.After Google resolves the outage, you can choose to eitherfail back to theprimary zone or make it the new failover zone.

Region outages

If a region outage occurs, you must wait for Google to resolve the outage andthen verify that the application works as expected. If you need robustnessagainst region outages, consider using the multi-regional deployment archetype.

Reference architecture

For a reference architecture that you can use to design a zonal deployment onCompute Engine VMs, seeSingle-zone deployment on Compute Engine.