CQRS
Command Query Responsibility Segregation — separate the write model from the read model so each can be optimised (and scaled) independently.
Coined by Greg Young (2010) as an extension of Bertrand Meyer's CQS principle. Commands change state, queries read — and they don't have to share a data model. Common shape: write into a normalised store, project denormalised read views (often Redis, Elasticsearch or materialised views).
Pairs naturally with event sourcing but doesn't require it. Cost: eventual consistency between write and read, plus more infrastructure. Only pays off when read/write patterns diverge sharply — otherwise overkill.