3.3.2.1. Fleet Management Services (Systems Manager, AWS Auto Scaling)

Managing hundreds of instances individually is impossible. Fleet management treats your entire instance population as a single manageable entity.

Systems Manager fleet capabilities:

Feature	Purpose	Scope
Fleet Manager	Visual dashboard of all managed instances	All instances
Run Command	Execute commands across the fleet	Tag/instance-based targeting
Patch Manager	Automated patching with compliance reporting	Patch group-based
State Manager	Enforce desired configuration	Association-based
Session Manager	Browser-based shell access (no SSH keys)	Individual instances
Inventory	Collect software/hardware metadata	All managed instances

# Run a command on all instances tagged Environment=Production
aws ssm send-command \
  --document-name "AWS-RunShellScript" \
  --targets "Key=tag:Environment,Values=Production" \
  --parameters 'commands=["df -h","free -m","uptime"]' \
  --comment "Health check across production fleet"

Auto Scaling fleet management:

Mixed instances policy: Combine On-Demand and Spot instances in the same ASG. Spot provides 60-90% cost savings for fault-tolerant workloads.
Instance refresh: Rolling replacement of all instances in an ASG (for AMI updates). Configure MinHealthyPercentage to maintain availability during refresh.
Warm pools: Pre-initialized instances in a stopped state, ready to launch in seconds during scale-out.

Exam Trap: SSM Session Manager provides browser-based shell access without opening port 22 or managing SSH keys. All sessions are logged to S3 and CloudWatch Logs for audit. If the exam asks about secure instance access without SSH, Session Manager is the answer — not a bastion host. This also works in private subnets with VPC endpoints for SSM.

Written byAlvin Varughese•Founder•15 professional certifications