> ## Documentation Index
> Fetch the complete documentation index at: https://headgate.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# PostgreSQL

> Reference backend with transactional application work and push notifications.

PostgreSQL is headgate's reference backend. Its admission query evaluates policy, claims
rows, and writes leases atomically. It also provides inspection, application transactions,
and `LISTEN/NOTIFY` wakeups.

<CodeGroup>
  ```rust Rust theme={"system"}
  let store = std::sync::Arc::new(
      headgate_postgres::PgStore::connect("postgres://localhost/headgate", 16)?
  );
  ```

  ```go Go theme={"system"}
  store, err := headgatepgx.Connect(ctx, "postgres://localhost/headgate")
  ```
</CodeGroup>

## Production notes

* Size the application-owned pool for handlers, API traffic, duties, and transactions.
* Notification connections are separate from ordinary query capacity.
* PgBouncer transaction pooling cannot preserve session-level notifications; polling
  remains supported.
* Schema qualification and multi-instance isolation are explicit.

<CardGroup cols={2}>
  <Card title="Connection budgets" icon="calculator" href="/docs/operations/connection-budget" />

  <Card title="Multiple installations" icon="boxes" href="/docs/operations/multi-instance" />
</CardGroup>