PAWS hub uses ToolsDB as it's primary database. This isn't entirely an appropriate use of ToolsDB, which is ideally used for Toolforge tools, and ToolsDB has become an increasingly unstable service in need of replacing anyway. PAWS has relatively simple database needs and the DB could be maintained much more easily than ToolsDB overall.
The ideal would be a to use T212595: [Feature request] Database as a Service (Trove) for Cloud VPS projects. However, if we get around to it first, a couple little instances running mariadb in the PAWS cloud-vps project would be just fine.