Compute Cost Optimization Strategy — AWS Developer (DVA-C02)
Spot vs Reserved vs On-Demand by Interruption Tolerance
'Fault-tolerant' and 'stateless batch' in a workload description are Spot-eligibility signals. 'Consistent baseline compute' points to Reserved Instances or Savings Plans. 'Short-lived, variable, or unpredictable' points to on-demand. Spot Instances receive a two-minute interruption notice via EC2 instance metadata before termination, giving fault-tolerant workloads time to checkpoint or drain. Spot fleets mitigate single-pool interruptions by spreading requests across multiple instance types and Availability Zones. A mixed-fleet Auto Scaling group combining On-Demand base capacity with Spot supplemental capacity balances cost reduction against interruption risk for workloads that tolerate occasional task restart.
What This Pattern Tests
The exam presents workload characteristics and tests pricing model selection. Spot Instances offer 60-90% savings for interruptible workloads — batch processing, CI/CD runners, data analytics. Compute Savings Plans offer 20-40% savings with flexibility across instance families, regions, and OS. EC2 Instance Savings Plans offer slightly deeper savings but lock to a specific instance family and region. Graviton3 instances provide ~25% better price-performance than comparable x86 instances. The trap is recommending Spot for a user-facing web tier (interruptions cause errors) or ignoring Graviton when the scenario mentions "optimize compute cost" for Linux workloads.
Decision Axis
Workload characteristics (interruptibility, predictability, architecture) determine pricing model. Spot for fault-tolerant, Savings Plans for steady, Graviton for ARM-compatible.
Associated Traps
More Top Traps on This Exam
Decision Rules
Determine whether a short-burst, episodic test workload (90 min active per invocation, 15-20 invocations per day) justifies a Reserved Instance commitment or whether on-demand CloudFormation stack provisioning or serverless compute eliminates idle spend more cost-effectively.
Domain Coverage
Difficulty Breakdown