Placement groups are logical groupings of EC2 instances that influence their physical placement on underlying hardware, allowing you to control instance proximity for low latency, high throughput, or fault isolation.

An EC2 Placement Group is a logical grouping that influences how instances are placed on underlying hardware, allowing users to control the proximity of instances for performance, high availability, or fault isolation. Placement groups are essential for applications requiring low latency (HPC, real-time analytics) or high resilience (distributed databases, critical microservices). Once created, you can launch instances into the placement group using the --placement-group parameter. Placement groups cannot be merged, and instances can be moved between groups only by stopping, modifying placement, and restarting.

Creating a Placement Group

Key Characteristics

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Placement groups are specific to a single Availability Zone, except for spread placement groups which can span multiple AZs
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Each placement group name must be unique within your AWS account and region
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You cannot merge placement groups or move instances between groups without stopping and restarting
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Placement groups can be created using AWS Management Console, CLI, or SDKs
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You can describe placement groups using aws ec2 describe-placement-groups