Placement Groups

A placement groups is a logical grouping of instances within a single Availability Zone.

Placement Groups are recommended for applications that benefit from low network latency, high network throughput, or both

Placement Groups Limitations 

Placement Group have the flowing limitations:

• A placement group can’t span multiple AZ’s
• Not all instance types support placement groups
• The name of specific placement group mus be unique within your AWS account
• Not all the instances types that can be lunched into a placement group can take full advantage of the 10 Gbps network

You can delete placement group if you no longer need. Before you can delete you placement group, you must terminate all instances that you lunched into the placement group .