A company runs EC2 instances 24/7 for a stable, predictable production workload and plans to do so for 3 years. They want the maximum possible discount and are comfortable committing to a specific instance type in a single region. Which purchasing option gives the highest discount?
- AOn-Demand Instances — no commitment discount; most expensive for steady-state workloads.
- BStandard Reserved Instances (3-year, All Upfront) — highest discount (up to 72% vs On-Demand) in exchange for a full upfront commitment to a specific instance type and region.✓ Correct
- CConvertible Reserved Instances — lower discount than Standard RIs due to added flexibility to change instance attributes.
- DSpot Instances — up to 90% discount but can be interrupted; not suitable for 24/7 production workloads.
Standard RIs offer the highest discount of all RI types. Paying All Upfront maximises savings compared to Partial Upfront or No Upfront. The trade-off: you're locked into a specific instance type, region, OS, and tenancy for 1 or 3 years. Compute Savings Plans offer similar savings with more flexibility but slightly lower maximum discount.
A company uses a mix of EC2 instance types and sizes, and frequently changes their compute needs. They want a significant discount over On-Demand without committing to specific instance families or regions. Which option provides this flexibility?
- AStandard Reserved Instances — locked to specific instance type, OS, and region.
- BOn-Demand Capacity Reservations — reserves capacity but provides no billing discount.
- CCompute Savings Plans — up to 66% savings, automatically applies to any EC2 instance regardless of family, size, OS, region, or tenancy; also covers Lambda and Fargate.✓ Correct
- DEC2 Instance Savings Plans — more flexible than Standard RIs but still locked to a specific instance family within a region.
Savings Plans types: (1) Compute Savings Plans — most flexible, applies to EC2/Lambda/Fargate anywhere. (2) EC2 Instance Savings Plans — highest discount after Standard RIs, locked to instance family + region. Both require a $/hour commitment for 1 or 3 years. Savings Plans are the modern replacement for RIs and are simpler to manage.
A company wants to run a fault-tolerant, stateless web tier that can scale down to zero during off-peak hours and does not require guaranteed availability. Which EC2 pricing model provides the lowest cost for this workload?
- AOn-Demand — no interruption, but more expensive than Spot for interruptible workloads.
- BReserved Instances — cost-efficient but instances are committed 24/7; wasteful for variable needs.
- CSpot Instances — up to 90% cheaper than On-Demand; ideal when the workload is stateless and can handle interruptions gracefully.✓ Correct
- DDedicated Hosts — the most expensive option, used for compliance/licensing requirements.
Spot Instances use spare AWS capacity at steep discounts. AWS can reclaim them with a 2-minute warning when capacity is needed. Best uses: stateless web servers, batch processing, CI/CD, big data analytics, containerised workloads, and ML training jobs. Use Spot with Auto Scaling Spot Fleet to handle interruptions automatically by launching replacement capacity.
A company suspects their EC2 instances are over-provisioned — running at 5–10% CPU utilisation consistently. Which AWS service analyses actual utilisation metrics and recommends right-sized instance types?
- AAWS Cost Explorer — shows cost trends and basic RI/Savings Plan recommendations but limited instance-level sizing analysis.
- BAWS Compute Optimizer — analyses 14 days of CloudWatch metrics and recommends optimal EC2 instance types, Lambda memory sizes, and EBS volume types.✓ Correct
- CAWS Trusted Advisor — provides general best practice checks including underutilised instances, but less detailed than Compute Optimizer.
- DAmazon CloudWatch — collects metrics but does not generate instance recommendations.
AWS Compute Optimizer uses ML to analyse CloudWatch metrics (CPU, memory, disk, network) over up to 14 weeks and recommends optimal configurations. It covers EC2 instances, Auto Scaling groups, EBS volumes, Lambda functions, ECS on Fargate, and RDS. Recommendations show projected cost savings and performance improvement estimates.
A company stores compliance log files in S3. Files are accessed daily for the first 30 days. After 30 days they are rarely accessed. They must be retained for 7 years. What is the MOST cost-effective S3 storage strategy?
- AStore all files in S3 Standard for 7 years — simple but very expensive for 6.9 years of rarely-accessed data.
- BDelete files after 90 days — violates the 7-year retention requirement.
- CS3 Standard for 30 days → S3 Standard-IA for 6 months → S3 Glacier Deep Archive for the remaining ~6.5 years (lowest storage cost at ~$0.00099/GB/month).✓ Correct
- DMove all files to S3 Glacier Deep Archive immediately — files need to be accessible for the first 30 days without the 12–48 hour retrieval delay.
S3 Glacier Deep Archive is the lowest-cost AWS storage class (~$0.00099/GB/month), designed for long-term retention of data accessed once or twice per year. Retrieval takes 12–48 hours. S3 Lifecycle Policies automate transitions between storage classes. The tiered approach: Standard (hot) → Standard-IA (warm) → Glacier Deep Archive (cold) optimises cost across the retention lifecycle.