In-Memory Driver

The in-memory driver stores events, checkpoints, and snapshots in plain JavaScript arrays and maps. It requires no external dependencies and works out of the box.

import { createEventStore, createAggregateRoot } from '@requence/event-sourcing/memory'

const eventStore = createEventStore({
  aggregateRoots: [userAggregateRoot],
})

When to use

Unit and integration tests — no database setup needed, tests run instantly.
Prototyping — focus on your domain logic before committing to a database.
Single-process applications — lightweight apps that don’t need durable persistence.

Configuration

import { createEventStore, createAggregateRoot } from '@requence/event-sourcing/memory'

const eventStore = createEventStore({
  // Required — one or more aggregate roots
  aggregateRoots: [user, project],

  // Optional — disable automatic initialization (default: true)
  autoInit: false,

  // Optional — callback invoked after events are appended
  onEventsAppended(events) {
    console.log(`${events.length} event(s) appended`)
  },

  // Optional — progress callbacks for projection replays
  onProjectionReplay: {
    begin(name) { console.log(`Replaying ${name}…`) },
    end(name) { console.log(`${name} replay complete`) },
  },

  // Optional — progress callbacks for process manager refreshes
  onProcessManagerRefresh: {
    begin(name) { console.log(`Refreshing ${name}…`) },
    end(name) { console.log(`${name} refresh complete`) },
  },

  // Optional — post-process events before they are appended
  postProcessEvent(event, aggregateRoot) {
    return event
  },
})

Features

The in-memory driver provides full support for all event store features:

Event storage with position tracking and concurrency checks
Checkpoints for projection and process manager catch-up
Aggregate root snapshots for fast stream rehydration
Projection snapshots with applied-count tracking
ConcurrencyError thrown when the expected stream version doesn’t match