Overview

OpenOutbox is a specification for implementing the transactional outbox pattern across different storages and message brokers.

This specification is organized into the following sections:

Foundations

• Introduction — Overview and purpose.
• Terminology and Concepts — Key definitions and actors.

Core Concepts

• Event Model — The structure of outbox records.
• Delivery Semantics — Guarantees and acknowledgement rules.
• Processing Lifecycle — State transitions and flow.

Technical Contracts

• Store Contract — Requirements for storage backends.
• Publisher Contract — Requirements for message dispatchers.

Reliability & Scale

• Retries and Failures — Error handling and terminal states.
• Ordering and Partitioning — Concurrency and sequence guarantees.

Management

• Operations and Replay — Inspection, recovery, and manual overrides.

The goal is to standardize outbox behavior independently from a specific database, broker, or framework.

Goals

• define a portable outbox contract
• separate semantics from implementation
• support multiple storage and broker backends
• make delivery guarantees explicit
• standardize ordering and partitioning behaviors
• enable conformance testing across implementations

Non-goals

• defining a single required database schema
• defining broker-specific wire protocols
• guaranteeing exactly-once delivery across all systems
• replacing broker-native semantics

Status

Draft