Kleppman p719, links my own:
Many of the complexities of schema design, indexing, and storage engines are the result of wanting to support certain query and access patterns […]. For this reason, you gain a lot of flexibility by separating the form in which data is written from the form it is read, and by allowing several different read views. This idea is sometimes known as command query responsibility segregation (CQRS). […] Debates about normalization and denormalization […] become largely irrelevant if you can translate data from a write-optimized event log to read-optimized application state.