---
title: "Overview"
description: "What a Queen deployment is made of: one stateless broker, one PostgreSQL, and the handful of environment variables that matter on the first day."
---

> Queen MQ documentation, for AI agents
> Complete self-contained summary of Queen MQ: https://queenmq.com/llms-brief.txt
> Fetch that first when the question is about the product rather than about this page.
> Index of all pages: https://queenmq.com/llms.txt

# Overview

A Queen deployment is one process and one database. The broker is a single stateless Rust binary
that serves HTTP on port 6632 and keeps every byte of state in PostgreSQL: no data directory to
back up, no coordination service, no sidecar, no message file format on disk.

Four parts, of which two are required:

- the `queen` broker, one process, run as one to three identical replicas
- PostgreSQL, the only source of truth: messages, offsets, the dedup index, queue configuration,
  dead letters
- the disk spool, node-local, where pushes land when PostgreSQL is unreachable
- `queen_proxy`, optional, a separate binary that fronts the broker with API keys, quotas and
  tenants

Nothing is installed into either required part. The DDL and the 27 stored-procedure files are
compiled into the binary and re-applied idempotently at every boot under an advisory lock, so
there is no migration step and no extension. The dashboard, `queenctl` and the PostgreSQL client
tools travel inside the same image.

A complete deployment, ready to verify:

```bash
docker network create queen
docker run -d --name queen-pg --network queen -e POSTGRES_PASSWORD=postgres postgres:16
docker run -d --name queen --restart on-failure:10 --network queen -p 6632:6632 -e PG_HOST=queen-pg -e PG_PASSWORD=postgres -v queen-spool:/var/lib/queen/buffers ghcr.io/queen-mq/queen:latest
curl -s http://localhost:6632/health
```

The only ordering requirement is a reachable PostgreSQL. Without one the broker fails its boot
loudly instead of starting half-working, which is what the restart policy is for: pasted as a
block, the third command lands while PostgreSQL is still initialising, and Docker brings the broker
back as soon as it can. Expect the `curl` to answer nothing on the first try and to answer within a
couple of seconds on the next. A broker that loses the database later answers 503 on `/health`
until it comes back.

## The variables of the first day

`PG_HOST`, `PG_PORT`, `PG_USER`, `PG_PASSWORD` and `PG_DATABASE` reach the database. `PG_USER` and
`PG_DATABASE` default to `postgres` and `PG_PORT` to 5432, so in a container the host and the
password are usually the whole of it.

`PORT` moves the HTTP listener off 6632. `DB_POOL_SIZE`, default 160, is the ceiling on concurrent
database work for one broker and has to fit inside `max_connections` across every replica.
`FILE_BUFFER_DIR` is where the spool lives: mount it, because it is replayed only from the same
directory.

Booleans are strict everywhere: `true/false`, `1/0`, `yes/no`, `on/off`, case-insensitive. Anything
else is a fatal boot error rather than a guess, and every boot prints the configuration the broker
actually resolved, secrets masked.

`JWT_ENABLED` is `false` by default, which means every route is served to every caller,
`/api/v1/system/*` included, and the broker has no HTTPS listener at all. Terminate TLS in front of
it and turn authentication on before it reaches a routable address.

Every variable the broker reads, with the default the code applies, is in
[the configuration reference](/reference/config).

## Where the rest lives

- [PostgreSQL](/deploy/postgres) — Version floor, privileges, pooling, and how to size the database that is the whole system.
- [Kubernetes](/deploy/kubernetes) — A reference manifest, with probes that do not restart brokers when the database blips.
- [Operations](/deploy/operations) — Retention, backup, upgrades, logs and metrics, and surviving a database outage.
- [High availability](/deploy/ha) — Replicas against one PostgreSQL, what the mesh carries, and the port that must be firewalled.
- [Security](/deploy/security) — The trust boundaries: authentication, TLS in front, TLS to PostgreSQL, payloads at rest.
- [Multi-tenant](/deploy/multi-tenant) — queen_proxy in front: tenants, API keys, quotas, metering and isolation.
- [Dashboard](/deploy/dashboard) — The operator UI the binary already serves on the port you opened.

The per-mechanism detail is reference material: [JWT and JWKS](/reference/security/jwt), [payload
encryption](/reference/security/encryption), [PostgreSQL TLS](/reference/security/postgres-tls),
[tenant endpoints](/reference/multi-tenant/endpoints), the [CLI](/reference/queenctl), the
[metrics](/reference/prometheus) and the [limits](/reference/limits).

One binary, one database, one port. Everything past that is something you chose to switch on.

Source: https://queenmq.com/deploy/index.mdx