A spread placement group places instances on distinct underlying hardware across multiple Availability Zones (or within a single AZ), providing the highest level of fault tolerance by isolating critical instances from each other.
A spread placement group distributes EC2 instances across distinct underlying hardware, ensuring that each instance runs on a separate rack with independent power and network connectivity. This provides the highest level of fault tolerance among placement group strategies, as a failure of one rack affects only that instance. Spread groups can span multiple Availability Zones, and within each AZ, you can launch up to 7 running instances per AZ. This limitation makes spread groups ideal for small-scale critical applications like master databases, bastion hosts, or core application servers that require maximum isolation.
Maximum of 7 running instances per Availability Zone
Can span multiple Availability Zones, increasing total capacity (e.g., 7 instances in AZ-A and 7 in AZ-B)
Provides the highest fault tolerance among placement group strategies
Ideal for critical applications requiring physical hardware isolation
Instances are placed on separate racks, each with independent power and network
Reduces impact of hardware failures to a single instance
Master database nodes requiring high availability
Bastion hosts or jump servers
Critical microservices that must remain operational despite hardware failures
Small-scale HA clusters (e.g., 3-node etcd or ZooKeeper)
Instances running compliance workloads requiring physical separation