Mixed practice exam 6

Explanation

Answer: A. S3 Intelligent-Tiering exists precisely for unknown or changing access patterns. It monitors object access and moves objects between a Frequent Access tier, an Infrequent Access tier after 30 days without access, and an Archive Instant Access tier after 90 days, then moves them straight back on access. Critically, AWS charges no retrieval fees for Intelligent-Tiering, so an unexpected access spike does not produce a surprise bill. The only additional charge is a small monthly monitoring and automation fee per object.

• B. S3 Standard-IA charges a per-GB retrieval fee, so an access spike on data the company assumed was cold produces exactly the surprise charge it wants to avoid. It also carries a 30-day minimum storage duration.
• C. Glacier Flexible Retrieval requires an explicit restore before objects can be read, imposes retrieval charges, and has a 90-day minimum storage duration, none of which suits unpredictable access.
• D. One Zone-IA lowers cost by reducing durability protection to a single Availability Zone, and it still charges retrieval fees. It addresses a different trade-off entirely.

Explanation

Answer: B. AWS charges for data transfer between Availability Zones in the same Region, and the charge applies to both the inbound and outbound side of the transfer. Communication between resources in the same Availability Zone over private IPv4 addresses is not charged. That gives the architect a real cost lever, though it has to be weighed against resilience, since collapsing tiers into one Availability Zone removes the fault isolation that multi-AZ deployment provides.

• A. Reversing the direction changes nothing, because the charge applies to inbound and outbound traffic for the resources involved.
• C. Cross-Availability Zone traffic within a Region is charged, so it is a legitimate and often significant line item for chatty application tiers.
• D. Using public IPv4 or Elastic IP addresses makes matters worse, not better. Traffic routed through those addresses is charged even between resources in the same Region, because it leaves through the internet gateway.

Explanation

Answer: C. AWS provides 100 GB of data transfer out to the internet free each month, and the allowance is aggregated across AWS services and Regions rather than granted per service. The AWS China and AWS GovCloud (US) Regions are excluded. Beyond the free allowance, outbound transfer is charged on a tiered scale in which the per-GB rate falls as monthly volume rises.

• A. The allowance is a standing monthly benefit, not a 12-month introductory offer, and it is 100 GB rather than 1 TB.
• B. Granting the allowance per service and per Region would multiply it many times over. AWS aggregates the 100 GB across services and Regions so an account receives it once per month.
• D. There is a standing free allowance, which is why small workloads frequently show no data transfer out charges at all.

Explanation

Answer: D. Retrieval latency, not the word 'Glacier', is what separates these classes. S3 Standard-IA and S3 Glacier Instant Retrieval both deliver millisecond first-byte latency on a normal GET request with no restore step. Glacier Instant Retrieval simply prices storage lower and retrieval higher, with a 90-day minimum storage duration, for archives that are rarely read but must appear instantly when they are.

• A. Both of these require an explicit restore. Glacier Flexible Retrieval returns data in minutes to hours depending on the retrieval tier, and Deep Archive within 12 hours for Standard or 48 hours for Bulk.
• B. S3 Standard-IA is millisecond-latency, but Glacier Flexible Retrieval is not, so the pair does not hold.
• C. S3 One Zone-IA is millisecond-latency, but Deep Archive is the slowest class AWS offers, so the pair does not hold.

Explanation

Answer: B. The first snapshot of an EBS volume is a full copy, but every subsequent snapshot stores only the blocks that changed since the previous one. Customers are billed for the actual data consumed rather than for the provisioned volume size multiplied by the number of snapshots. This is why a frequent snapshot schedule on a slowly changing volume is much cheaper than the snapshot count alone would suggest, and it is also why deleting one snapshot in a chain does not free as much storage as customers often expect.

• A. Only the first snapshot is a full copy. Charging for the full volume on every snapshot would make frequent backup schedules prohibitively expensive.
• C. Snapshots incur an ongoing per-GB-month storage charge for the data they hold, so they must be lifecycle-managed to control cost.
• D. Snapshot storage is charged regardless of Region. Copying snapshots to another Region adds data transfer charges on top.

Explanation

Answer: A. Amazon RDS has its own Reserved DB Instance construct with 1-year and 3-year terms and All Upfront, Partial Upfront, and No Upfront payment options, offering savings of up to 69% compared with On-Demand rates. These reservations are purchased through Amazon RDS and apply only to RDS DB instances. For most engines, including MySQL, MariaDB, PostgreSQL, and Aurora, RDS reservations are size-flexible within an instance family.

• B. Spot pricing is not offered for Amazon RDS. Spot capacity can be reclaimed at short notice, which is incompatible with a managed relational database.
• C. EC2 Reserved Instances apply only to EC2 instance usage. They do not cover managed database services, which have their own commitment mechanisms.
• D. RDS supports committed-use pricing through Reserved DB Instances, so On-Demand is not the only option available.

Explanation

Answer: B and C. Both actions attack the two places AWS actually meters transfer. Serving through Amazon CloudFront removes the origin-to-CloudFront charge entirely and moves egress onto CloudFront's own pricing, which is generally lower per GB for high volumes. Keeping chatty instances in one Availability Zone and addressing them by private IPv4 avoids the per-GB cross-Availability Zone charge that applies in both directions. Both must still be weighed against resilience requirements.

• A. Traffic that leaves through a public IPv4 or Elastic IP address is charged even between resources in the same Region, and public IPv4 addresses carry their own hourly charge. This would increase cost.
• D. Copying data to a second Region adds inter-Region data transfer charges plus a second copy of the storage. It may improve latency or resilience, but it does not reduce transfer cost.
• E. Reserved Instances discount compute, not data transfer. Data transfer is billed separately from instance hours under every purchasing option.

Explanation

Answer: B. AWS states that more than 30 services include monthly usage limits that are always free, and that these apply on both the Free and Paid account plans. AWS Lambda's 1 million monthly requests and 400,000 GB-seconds are a well-known example. Always-free offers do not expire with the account's age, which distinguishes them from short-term trials and from the sign-up credits that come with a new account.

• A. Both account plans receive always-free offers. Restricting them to the Free plan would penalize customers who move to pay-as-you-go pricing.
• C. AWS Organizations membership is unrelated to always-free usage limits. Standalone accounts receive them as well.
• D. A 12-month window describes the legacy free tier model that AWS restructured. Always-free offers, by definition, do not expire after a fixed period.

Explanation

Answer: D. Under the restructured AWS Free Tier, the Free account plan provides USD 100 in sign-up credits plus the opportunity to earn up to USD 100 more by completing activities, and it runs for six months or until the credits are exhausted, whichever comes first. When the plan expires the account closes automatically, and AWS retains the content for 90 days during which the customer can upgrade to a Paid plan. The Free plan also restricts access to certain features, including Savings Plans and Reserved Instances.

• A. The 12-month model describes the legacy free tier that AWS replaced. It also never covered all AWS services, only specific offers within stated limits.
• B. Credits are applied against usage as it is incurred rather than refunded, and the Free plan does not bill at standard rates while it is active.
• C. The Free plan gives access to a selected set of services, not every service, and the plan itself expires after six months. Only the always-free offers continue indefinitely, and those apply on the Paid plan.

Explanation

Answer: D. S3 Glacier Instant Retrieval is built for exactly this profile: long-lived archives that are rarely accessed but must come back immediately. It delivers millisecond first-byte latency with no restore step, at a storage rate well below S3 Standard-IA. The costs to plan for are the 90-day minimum storage duration charge and the per-GB retrieval fee, so the class only pays off when objects genuinely stay for months and are read infrequently.

• A. Glacier Flexible Retrieval requires an explicit restore and returns data in minutes to hours. Even Expedited retrieval at one to five minutes fails a millisecond requirement.
• B. S3 Standard would meet the latency requirement, but at roughly six times the per-GB storage rate of Glacier Instant Retrieval it is the wrong economics for data read a few times a year.
• C. Deep Archive returns objects in 12 to 48 hours, which cannot satisfy a clinician waiting on an image.