This article explains the Command Query Responsibility Segregation (CQRS) design pattern, which separates read and write operations in database management. It discusses the benefits and challenges of CQRS, including data replication methods and offers a demo application example using a voting system.

UnisonDB is an open-source, log-native database designed for edge computing and AI applications. It uses a combination of Write-Ahead Logging and B+Tree storage for fast, consistent data replication across multiple nodes, enabling low-latency operations. The system merges database functions with streaming capabilities, allowing for instant updates and real-time responsiveness.

This article outlines key engineering insights gained from building a database replication tool for Amazon RDS Postgres using Rust. It addresses challenges like compatibility issues, deployment complexities, and the need for proactive network management. The authors stress the importance of customizing solutions for the specific constraints of managed environments.

pgactive is a PostgreSQL extension designed for active-active database replication, allowing multiple instances within a cluster to accept changes simultaneously. This approach enables various use cases, such as multi-region high availability and reducing write latency, but requires applications to manage complexities like conflicting changes and replication lag. Logical replication, introduced in PostgreSQL 10, is a key component for implementing this topology, while additional features are necessary for full support.

Postgres replication slots utilize two log sequence numbers (LSNs) — confirmed_flush_lsn and restart_lsn — to manage data streaming and retention effectively. The confirmed_flush_lsn indicates the last acknowledged data by the consumer, while the restart_lsn serves as a retention boundary for WAL segments needed for ongoing transactions. Understanding these differences is essential for troubleshooting replication issues and optimizing WAL retention in production environments.