Mistakes we made adopting event sourcing and how we recovered

In an event-sourced architecture, components record a history of events that occurred to the entities they manage, and calculate the state of an entity from the sequence of events that relate to it. Instead the application computes the current state from the event history when the entity is loaded from the database. The application still maintains a “projection” of the current entity states, but treats the projection as a read-through cache, used to optimise loading entities, so that it doesn’t have to load all of an entity’s events on every transaction, and to select subsets of the currently active entities, so that it doesn’t have to load all events of all entities.

Source: natpryce.com