Cost

Your app writes 2 TB/month of logs that are queried heavily for 7 days, rarely after 30, and must be kept 7 years. Which S3 setup is most cost-effective?

S3 storage classes trade cheap storage for slow, sometimes paid retrieval. When you already know how access drops off with age, the cheapest setup is a lifecycle rule that walks the data down the tiers as it ages. A single class overpays, and Intelligent-Tiering solves a problem this question doesn't have.

A company runs a business-critical application in one AWS Region. The disaster recovery plan requires a recovery time objective of 10 minutes and a recovery point objective of 1 minute in a second Region. The company wants to avoid paying for a full duplicate of the production fleet. Which disaster recovery strategy should a solutions architect choose?

RTO and RPO in minutes rule out backup and restore and pilot light, because both require standing infrastructure up before traffic can move. Warm standby keeps a scaled-down copy always running, which is what buys minutes instead of hours without paying for a second full fleet.

A company stores analytics datasets in Amazon S3. Access is unpredictable: some datasets are queried daily for months, others are never opened again after the first week, and the team cannot tell which is which in advance. All objects are larger than 1 MB and must remain available for immediate retrieval. Which approach is MOST cost-effective?

Lifecycle rules are the cheapest option when access falls off predictably with age. When nobody can predict it, S3 Intelligent-Tiering is the class designed for exactly that: it moves each object between tiers on its own access pattern, with no retrieval fees and no minimum storage duration.

A company runs a steady production workload on Amazon EC2 that has not changed size in two years and is expected to continue for at least three more. The team occasionally changes instance family as new generations are released, and is also beginning to move some services to AWS Fargate. The company wants the largest possible discount without giving up that flexibility. Which purchasing option should a solutions architect recommend?

Predictable long-running usage should never sit on On-Demand pricing. Compute Savings Plans give the deepest commitment discount while staying flexible across instance family, size, Region and even across EC2, Fargate and Lambda, which is what the stem's flexibility requirement is asking for.

A nightly batch job renders video segments. The work is split into thousands of independent tasks, any task can be retried safely if it fails, and the job must finish before 06:00 but has no other timing constraint. The company wants to minimise compute cost. Which approach should a solutions architect recommend?

Independent, retryable tasks with a loose deadline is the definition of an interruption-tolerant workload, and that is what Spot Instances are for. Spreading the request across several instance types and Availability Zones is what keeps a Spot fleet from being reclaimed all at once.

A VPC spans three Availability Zones, each with a private subnet running application instances. All three private subnets route internet-bound traffic through a single NAT gateway in the first Availability Zone. A solutions architect must remove the dependency on that one Availability Zone and reduce cross-Availability Zone data transfer charges. What should the architect do?

A NAT gateway lives in one Availability Zone, so routing all three subnets through it creates both a single point of failure and a cross-zone data transfer charge on most of the traffic. Deploying one NAT gateway per Availability Zone fixes both problems at once.

A development team uses several Amazon RDS for MySQL instances that are only needed during working hours on weekdays. The team wants to stop paying for them outside those hours with the least possible engineering effort, and the databases must retain their data and endpoints between sessions. Which solution meets these requirements?

Stopping an RDS instance removes the instance-hour charge while keeping the data, the endpoint and the configuration. The catch worth knowing is the seven-day limit: RDS restarts a stopped instance automatically after seven consecutive days, so a weekday schedule fits and a long shutdown does not.