MySQL 5.7 Release Notes
The following examples are typical use cases for Group Replication.
Elastic Replication - Environments that require a very fluid replication infrastructure, where the number of servers has to grow or shrink dynamically and with as few side-effects as possible. For instance, database services for the cloud.
Highly Available Shards - Sharding is a popular approach to achieve write scale-out. Use MySQL Group Replication to implement highly available shards, where each shard maps to a replication group.
Alternative to Source-Replica replication - In certain situations, using a single source server makes it a single point of contention. Writing to an entire group may prove more scalable under certain circumstances.
Autonomic Systems - Additionally, you can deploy MySQL Group Replication purely for the automation that is built into the replication protocol (described already in this and previous chapters).