# Transactional outbox

> A write and its event land in one transaction, and a relay publishes it: the copies stop diverging when a publish fails.

## Prerequisites

Research these first: [Message queues](https://wiki.playquorum.dev/research/queues.md).

## Engineering terms

- [Transactional outbox](https://wiki.playquorum.dev/glossary/transactional-outbox.md)
- [At-least-once delivery](https://wiki.playquorum.dev/glossary/at-least-once-delivery.md)

## Facts

Transactional outbox
- **Track:** Data
- **Era:** [Series B](https://wiki.playquorum.dev/eras/series-b.md)
- **Cost:** 7.00k 7.00k
- **Requires:** [Message queues](https://wiki.playquorum.dev/research/queues.md)

## See also

- [Research tree](https://wiki.playquorum.dev/research.md)

Source: https://wiki.playquorum.dev/research/outbox