Primary-Replica
A replication topology where one node (primary) handles writes and replicates changes to one or more read-only replicas. The foundation of most database scaling strategies.
What is Primary-Replica?
A replication topology where one node (primary) handles writes and replicates changes to one or more read-only replicas. The foundation of most database scaling strategies.
Primary-Replica is a intermediate-level concept that sits in the Data Replication & Distribution 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 "Primary-Replica" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Primary-Replica lessonRelated lessons
Lessons that touch on Primary-Replica as part of a larger topic.
Master-Slave Replication
The most common replication topology, one writer, many readers, and the trade-offs that come with it
foundation · database fundamentals
Read Replicas
Scaling reads by replicating data to follower databases, primary-replica architecture and replication lag
foundation · database fundamentals
See also
Related glossary terms you might want to look up next.
Read Replica
A copy of your database that handles read queries, reducing load on the primary database. Writes still go to the primary and replicate out.
Replication
Keeping copies of the same data on multiple servers. Improves read performance and provides fault tolerance if one server goes down.
Leader Election
The process of choosing one node in a cluster to coordinate actions. If the leader fails, a new one is elected. Used by Kafka, ZooKeeper, and etcd.