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A solutions architect is designing a solution where users will be directed to a backup static error page if the primary website is unavailable. The primary website’s DNS records are hosted in Amazon Route 53 where their domain is pointing to an Application Load Balancer (ALB).
Which configuration should the solutions architect use to meet the company’s needs while minimizing changes and infrastructure overhead?
A. Point a Route 53 alias record to an Amazon CloudFront distribution with the ALB as one of its origins. Then, create custom error pages for the distribution.
B. Set up a Route 53 active-passive failover configuration. Direct traffic to a static error page hosted within an Amazon S3 bucket when Route 53 health checks determine that the ALB endpoint is unhealthy.
C. Update the Route 53 record to use a latency-based routing policy. Add the backup static error page hosted within an Amazon S3 bucket to the record so the traffic is sent to the most responsive endpoints.
D. Set up a Route 53 active-active configuration with the ALB and an Amazon EC2 instance hosting a static error page as endpoints. Route 53 will only send requests to the instance if the health checks fail for the ALB.
Correct Answer: B Section: (none) Explanation
Use an active-passive failover configuration when you want a primary resource or group of resources to be available the majority of the time and you want a secondary resource or group of resources to be on standby in case all the primary resources become unavailable. When responding to queries, Route 53 includes only the healthy primary resources. If all the primary resources are unhealthy, Route 53 begins to include only the healthy secondary resources in response to DNS queries.
To create an active-passive failover configuration with one primary record and one secondary record, you just create the records and specify Failover for the routing policy. When the primary resource is healthy, Route 53 responds to DNS queries using the primary record. When the primary resource is unhealthy, Route 53 responds to DNS queries using the secondary record.
How Amazon Route 53 averts cascading failures
As a first defense against cascading failures, each request routing algorithm (such as weighted and failover) has a mode of last resort. In this special mode, when all records are considered unhealthy, the Route 53 algorithm reverts to considering all records healthy.
For example, if all instances of an application, on several hosts, are rejecting health check requests, Route 53 DNS servers will choose an answer anyway and return it rather than returning no DNS answer or returning an NXDOMAIN (non-existent domain) response. An application can respond to users but still fail health checks, so this provides some protection against misconfiguration.
Similarly, if an application is overloaded, and one out of three endpoints fails its health checks, so that it’s excluded from Route 53 DNS responses, Route 53 distributes responses between the two remaining endpoints. If the remaining endpoints are unable to handle the additional load and they fail, Route 53 reverts to distributing requests to all three endpoints.
Reference: https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/dns-failover-types.html https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/dns-failover-problems.html
A solutions architect is designing a high performance computing (HPC) workload on Amazon EC2. The
EC2 instances need to communicate to each other frequently and require network performance with low latency and high throughput.
Which EC2 configuration meets these requirements?
A. Launch the EC2 instances in a cluster placement group in one Availability Zone.
B. Launch the EC2 instances in a spread placement group in one Availability Zone.
C. Launch the EC2 instances in an Auto Scaling group in two Regions and peer the VPCs.
D. Launch the EC2 instances in an Auto Scaling group spanning multiple Availability Zones.
Correct Answer: A Section: (none) Explanation
Explanation: Placement groups
When you launch a new EC2 instance, the EC2 service attempts to place the instance in such a way that all of your instances are spread out across underlying hardware to minimize correlated failures. You can use placement groups to influence the placement of a group of interdependent instances to meet the needs of your workload. Depending on the type of workload.
Cluster – packs instances close together inside an Availability Zone. This strategy enables workloads to achieve the low-latency network performance necessary for tightly-coupled node-to-node communication that is typical of HPC applications.