CQRS
Command Query Responsibility Segregation: using different models for reading and writing data. Reads and writes have different performance needs, so separate them.
What is CQRS?
Command Query Responsibility Segregation: using different models for reading and writing data. Reads and writes have different performance needs, so separate them.
CQRS is a advanced concept that sits in the Distributed Systems Core area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "CQRS" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn CQRS in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the CQRS lessonRelated lessons
Lessons that touch on CQRS as part of a larger topic.
Event Sourcing
Store events instead of state, rebuild any point in time from the log of what happened
advanced · distributed systems core
Data Aggregation
Combine data from multiple sources into a unified view, building the single source of truth
intermediate · data governance compliance
Command Bus
Route explicit instructions to the one handler responsible for executing them
intermediate · messaging event systems
Event-Driven Architecture
Build systems where everything reacts to events, the architecture powering Netflix, Uber, and LinkedIn at massive scale
intermediate · messaging event systems
Command Pattern
Encapsulate requests as objects, enabling undo, queuing, logging, and distributed task execution
intermediate · microservices architecture
See also
Related glossary terms you might want to look up next.
Event Sourcing
Storing every state change as an immutable event instead of just the current state. You can rebuild any past state by replaying events.
Saga Pattern
A way to manage distributed transactions across microservices using a sequence of local transactions with compensating actions for rollback.
Microservices
An architecture where an application is split into small, independent services that communicate over the network. Each service owns its own data and can be deployed separately.