System Design Fundamentals | Pt 5 | Database replication

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Database replication is the process of copying data from one database to another, in order to ensure that multiple copies of the same data are available for redundancy, availability, and scalability. Replication can be synchronous or asynchronous, and can be implemented in various ways depending on the specific needs and requirements of the system.

In a typical database replication scenario, a master database is designated as the primary source of data, and one or more replica databases are created to serve as secondary copies of the data. The replica databases are usually located in different geographic locations or on different servers, to ensure that the data is highly available and can be accessed by users even if the primary database is unavailable due to maintenance, outage, or disaster.

Replication can be implemented in different ways, including:

1. Snapshot replication: This type of replication involves taking a complete copy of the master database and copying it to the replica database. This is a one-time operation that is typically used for initial data synchronization.

2. Transactional replication: This type of replication involves copying individual transactions from the master database to the replica database as they occur. This ensures that the replica database is always up to date with the latest changes to the data.

3. Merge replication: This type of replication involves merging changes made to the master database and replica database, in order to ensure that both databases have the same data.

4. Peer-to-peer replication: This type of replication involves creating multiple copies of the database that can act as both masters and replicas, allowing data to be distributed across multiple nodes for scalability and fault tolerance.

Replication can provide several benefits, including improved availability, increased scalability, and improved disaster recovery capabilities. It can also help ensure that data is consistent across multiple locations, and can provide a mechanism for load balancing and performance optimization. However, replication can also be complex to implement and maintain, and can introduce data consistency and synchronization challenges that need to be carefully managed.