Event Sourcing and CQRS with Node.js

Event Sourcing stores all changes to application state as a sequence of events. CQRS (Command Query Responsibility Segregation) separates the read and write models into different services/databases.

In Event Sourcing, you don't store the 'current state'. Instead, you store a sequence of events. CQRS complements this: the 'Write' side appends events to an 'Event Store', and a 'Read' side projects those events into a specialized DB optimized for queries.