> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tensor9.com/llms.txt
> Use this file to discover all available pages before exploring further.
# PostgreSQL
> Customer-provided PostgreSQL database in place of default-shipped PostgreSQL
If your origin stack uses PostgreSQL as its relational store, your customer can supply their own PostgreSQL instance (RDS, Cloud SQL, Aurora, self-hosted, etc.) and the compiler will emit a deployment stack that talks to it instead of provisioning a default-shipped database.
## What the customer provides
| Field | Purpose |
| ------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- |
| **Hostname** | The `host` (or `host:port` if non-default) of the PostgreSQL endpoint. |
| **Database name** | The PostgreSQL database the appliance's services should connect to. |
| **Username** | The role the appliance authenticates as. |
| **Password (or IAM role / managed-identity reference)** | The credential for the role. The appliance can use a static password or, where supported, an IAM-backed token. |
| **CA certificate** *(optional)* | The trust anchor for the PostgreSQL server's TLS certificate when the customer uses a private CA. |
The customer is responsible for creating the database, granting the appliance role the privileges it needs, and applying any schema migrations your application requires.
## What changes in the deployment stack
When customer-provided PostgreSQL is selected, the compiler:
* Drops the default-shipped PostgreSQL instance from the deployment stack (no RDS instance, no managed-instance provisioning, no automated backups).
* Wires the appliance's services to the customer's hostname and database.
* Injects the customer's credentials as secrets the services read at startup.
Your application code does not change. The connection string changes; the SQL the application emits does not.
## What the customer takes on
When your customer brings their own PostgreSQL, they own:
* Provisioning, instance sizing, and capacity planning.
* Backup, retention, and restore. Point-in-time recovery is the customer's PostgreSQL provider's feature, not Tensor9's.
* Patching and version upgrades. The customer's PostgreSQL major version must remain compatible with your application's requirements.
* High availability, read-replica topology, and failover.
* Connection pooling, if the appliance's connection count exceeds what the customer's deployment can handle directly.
* Monitoring, alerting, and incident response for the PostgreSQL instance itself.
## What stays your responsibility
* All application-level database concerns: schema design, query performance, application-managed migrations, data correctness.
* Your services continue to be observable through Tensor9's normal mechanisms (logs, metrics, traces) even though the database isn't.
* [Operations](/fundamentals/operations) commands that operate on the appliance's services still work normally. Operations commands cannot reach into your customer's PostgreSQL.
## Authentication and rotation
The username and password (or IAM role / managed-identity reference) are stored as [Customer-Supplied Secrets](/fundamentals/secrets#secret-ownership-models) - Tensor9 has no visibility into the underlying value. The appliance reads them at startup and on connection-pool establishment.
Two rotation paths:
* **Static password**: rotate the password in the customer's secret store and restart the affected services so they reconnect with the new credential.
* **IAM-backed auth** (RDS IAM, Cloud SQL IAM): the appliance assumes the customer-supplied IAM role at runtime and the underlying STS token is refreshed automatically (15-minute TTL on AWS). The customer rotates the role / policy, not the credential.
## Where this fits
This page is one of the services covered by [Customer-Provided Services](/customizations/customer-provided-services). For automatic cross-cloud substitution (RDS → Cloud SQL based on form factor), see [Service equivalents](/fundamentals/service-equivalents).