---
title: "What Queen MQ is"
description: "A partitioned message queue that stores everything in PostgreSQL, gives every entity its own ordered lane, and runs as one stateless binary."
---

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

# What Queen MQ is

Queen MQ is a message queue that keeps its data in PostgreSQL. A queue is split into
**partitions** (one per entity, created the first time you push to it), and each partition
is a strictly ordered lane that a consumer group drains independently. Ten thousand
partitions cost ten thousand index rows, not ten thousand log files or ten thousand
processes, and a consumer stuck on one lane never blocks another.

Everything else follows from that choice. The broker is one stateless Rust binary that
holds no cluster membership and no partition assignments, so you scale it by starting
another copy against the same database. Clients speak plain HTTP and hold no coordination
state either, which means there is no rebalancing protocol to wait out when a worker
restarts. The durability, backup and replication story is whatever your PostgreSQL
already does.

- [Quickstart](/start/quickstart) — A broker, a queue, and a message you push and consume, in about five minutes.
- [Why Queen exists](/start/why) — The head-of-line problem it was built for, and the eight design choices that follow.
- [Limits and non-goals](/start/limits) — What Queen does not do, what it deliberately refuses to do, and where the sharp edges are.
- [Compared to Kafka, RabbitMQ, SQS and pgmq](/start/compare) — Architectural differences, stated without performance claims we have not measured.

## Where to go next

The rest of the site is organised by what you are trying to do.

| If you want to | Read |
| --- | --- |
| Write an application against Queen | [Use Queen](/use): the model, the SDKs, the HTTP API, worked examples |
| Run Queen yourself | [Self-hosting](/selfhost): deployment, PostgreSQL, high availability, security, operations |
| Know how it works inside | [Internals](/internals): segments, offsets, the push and pop paths, the schema |
| Look one thing up | [Reference](/reference): routes, environment variables, metrics, client APIs |
| See what it does under load | [Benchmarks](/benchmarks): the runs, their configuration, and their raw output |

## What you get

- **One ordered lane per entity, with no preallocation.** Partitions are logical: they are
  created on first push and cost rows, not files or processes.
- **Consumer groups with replay.** Each group has its own cursor per partition and can be
  moved back to a timestamp or forward to the end.
- **Acknowledgement that is an offset commit.** Acking a message commits the cursor past
  it, so there is no per-message delivery state to store or clean up.
- **Transactional handoff.** Acking one message and pushing the next stage's message happen
  in a single PostgreSQL transaction.
- **Exact, windowed deduplication.** A `transactionId` you supply makes a push idempotent
  within a configurable window, enforced inside the database rather than in a cache.
- **A dead-letter queue, tracing, and a dashboard**, all served by the same binary.
- **Five language SDKs, an operator CLI, and a plain HTTP API**, so anything that can make an
  HTTP request is a first-class client.

## What this documentation promises

Queen's published documentation used to describe an earlier C++ broker; version 1.0 is a
Rust rewrite on a new storage engine, and this site was written from the current source.
Three rules hold everywhere on it:

- **Route tables, configuration references and metric lists are generated from the code**
  at build time, so they cannot drift into describing endpoints that do not exist.
- **Code samples are extracted from files the test suite executes.** Each one names the
  file it came from.
- **Numbers name their run.** A throughput figure without an archived artifact recording
  the configuration that produced it does not get published here.

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