Active-Active geo-distribution (CRDTS-based)

An Active-Active architecture is a data resiliency architecture that distributes the database information over multiple data centers via independent and geographically distributed clusters and nodes. It is a network of separate processing nodes, each having access to a common replicated database such that all nodes can participate in a common application ensuring local low latency with each region being able to run in isolation.

Active-Active Architecture or an Active-Active Geo-Distributed topology is achieved by implementing CRDTs (conflict-free replicated data types) in Redis Enterprise using a global database that spans multiple clusters. This is called a “conflict-free replicated database” or “CRDB.”

CRDB provides three fundamental benefits over other geo-distributed solutions:

• It offers local latency on read and write operations, regardless of the number of geo-replicated regions and their distance from each other.
• It enables seamless conflict resolution (“conflict-free”) for simple and complex data types like those of Redis core.
• Even if most of the geo-replicated regions in a CRDB (for example, 3 out of 5) are down, the remaining geo-replicated regions are uninterrupted and can continue to handle read and write operations, ensuring business continuity.

Deployments & topologies

A CRDB is a database that is created across multiple Redis Enterprise clusters, which typically reside in different data centers around the world. The database in each one of the participating clusters is called a “CRDB instance.” As long as a CRDB dataset fits into the CRDB instance memory, each CRDB instance can be configured differently-composed from a different number of shards and run on a different number or type of cluster nodes

Furthermore, one CRDB instance may run on a multi-availability-zone (AZ) cluster configuration with high availability and data persistence enabled. A second CRDB instance may run on a single-AZ cluster configuration without high availability or data persistence. These CRDBs can run simultaneously in any cloud environment, including Google Cloud, Azure, and AWS. This increased flexibility optimizes infrastructure costs and database performance for your particular use case.

An application that uses a CRDB is connected to the local CRDB instance endpoint. Bi-directional database replication is used between all CRDB instances in a mesh-like topology, i.e., all writes by the application to a local instance are replicated to all other instances, as illustrated here: