Decide what data a prototype can afford to lose
Google Cloud introduced AlloyDB Express in preview on November 4 for developers building prototypes and applications with coding agents. Its PostgreSQL 18 configuration can pause compute when idle, but the operational limits make the choice more consequential than simply choosing a smaller database.
The documentation specifies a single zonal instance and a 20 GB storage ceiling. Writes stop when that ceiling is reached. Express has no automated or on-demand backups, point-in-time recovery, regional high availability, or service-level agreement. CGH’s assessment is that teams should define how they will recreate test data before letting an agent use it for ongoing development.
Check the free allowance and the deployment region
Google describes compute billing by the second and a monthly allowance of 50 compute units plus 2 GB of storage per billing account for the first 12 months. Storage remains billable while an instance is idle. Pausing compute therefore does not make a retained database cost-free.
The Express overview lists seven regions, including us-west1 and europe-west2, with the remaining five in Asia and Australia. Teams should use that product-specific list when planning a deployment. The wider AlloyDB region list does not establish Express availability everywhere.
Upgrading changes the running-cost model
Google documents an in-place upgrade that preserves data, schemas, extensions, credentials and networking settings. The move turns off scale-to-zero and changes the instance to always-on AlloyDB billing. A one-vCPU instance in a region without C4A support must first be resized to two vCPUs.
The Express overview says returning from AlloyDB to Express is unsupported. Teams evaluating the upgrade should therefore check the resulting capacity, billing and recovery configuration before confirming it.
One documentation discrepancy also deserves attention. The launch blog lists Terraform among provisioning options, while the current Express overview lists Terraform and Config Connector as unsupported. CGH could not resolve that difference and recommends verifying the supported interface before designing automated setup around it. CGH reviewed public documentation without provisioning or testing an instance.