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Overview

EventCatalog supports different types of messages (commands, events and queries).

  • Commands
    • Commands are messages that represent intent, commands can be rejected in distributed systems.
  • Events
    • Events are a type of message that represent immutable facts.
  • Queries
    • Queries are a type of message that represent requests for information.

Linking messages to services, domains and channels​

  • Messages can be sent (producer) or received (consumer) by services, domains or be totally independent.
  • You can also route messages through one or more channels.

Where do messages live?​

Messages can live anywhere in your catalog, at the service level or domain level.

Example of a message living at the service level

Here we have the OrderPlaced message living at the service level.

services/
  Orders/
    events/
      OrderPlaced/
        index.mdx

Example of a message living at the domain level

Here we have the OrderPlaced message living at the domain level.

domains/
  Orders/
    events/
      OrderPlaced/
        index.mdx
You can reference messages from anywhere in your catalog

It does not matter where you store your messages, you can reference them from anywhere in your catalog. Your domains and services will reference them by their id and optionally the version. EventCatalog will resolve the message.