Database

Database Replication

DatabaseScalingAvailabilitySystem Design

Database replication is the frequent electronic copying of data from a database in one computer or server to a database in another so that all users share the same level of information.

Replication Strategies

Asynchronous

Leader acknowledges write immediately. Replicates to followers in background.

Fast WriteLag Possible

Synchronous

Leader waits for followers to acknowledge write before confirming to client.

No Data LossSlower

Leaderless

No single leader. Read/write to multiple nodes (Quorum). Handles node failures well.

High AvailComplex

Replication Flow

Visualize how data propagates across nodes

👤 Client Application

⬇

Client sends write request (v101) to Leader

Leader writes v101 locally

Leader acknowledges Client ("Success!")

Leader sends replication log to Follower 1

Leader sends replication log to Follower 2

Follower 1 updates to v101

Follower 2 updates to v101 (Eventual Consistency)

Architecture Comparison

Mode	Active Replication	Scaling Profile	Complexity	Best Use Case
Single-Leader	Yes	Read Only	Low	Web apps, CMS
Multi-Leader	Yes	Read/Write	High	Global apps, Offline clients
Leaderless	Yes	High Avail.	Med	Available-first (DynamoDB)

Resources

Title	Type	Link
Designing Data-Intensive Applications (DDIA)	book	Open
PostgreSQL Replication Guide	web	Open
MongoDB Replica Sets	web	Open

Guide Contributors

ObydulSenior Software Engineer

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