> For the complete documentation index, see [llms.txt](https://docs.ionos.com/cloud/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ionos.com/cloud/api-reference/databases/postgresql-v2/clusters.md). # Clusters A PostgreSQL (PG) cluster is a unified group of one or more interconnected database instances. It consists of a single primary instance that handles all write operations, along with optional standby replicas that provide high availability. This entity represents the entire logical unit, allowing for the unified management of all its nodes and configurations. Credentials are managed through the cluster resource and are used to provision and manage the cluster's database users. Customers can connect directly to the cluster using standard PostgreSQL tools to create additional users, databases, and access grants. When credentials are supplied, the behavior is additive: a new `username` creates a new user with cluster-wide access granted to the specified `database` — the previous user is preserved; a new `database` creates a new database and grants the specified user access to both the new and any previously accessible databases; an existing `username` updates the user's password. Unlike other cluster fields, omitting the `credentials` field leaves all existing users and databases unchanged rather than clearing them. This tag groups all operations for clusters. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.ionos.com/cloud/api-reference/databases/postgresql-v2/clusters.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.