event-contract-design

What problem does it solve?

It prevents misaligned producer/consumer expectations in asynchronous messaging by making event envelopes, schemas, ordering, replay, and compatibility rules explicit so integrations don’t degrade into shared folklore.

Core Features & Use Cases

• Producer/Consumer Ownership & Purpose: Clarifies who publishes an event, who relies on it, and why it exists.
• Event Envelope + Payload Schema: Specifies the machine-readable contract for envelope fields and payload requirements (including required, optional, nullable, and deprecated fields).
• Compatibility, Versioning, and Replay Semantics: Documents how events evolve safely (additive vs breaking), how correlation/causation cross boundaries, and what consumers should expect during replay and dead-letter scenarios.
• Contract Fixtures + Verification: Includes positive and negative fixtures suitable for contract testing and deterministic validation.

Quick Start

Use event-contract-design to define the publish/consume contract for a new OrderPaid async event, including envelope fields, payload schema rules, idempotency, ordering, replay, dead-letter behavior, and versioning compatibility.