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AWS

AWS Interview Questions and Answer Part – 8

January 11, 2020 comments off

You are designing a new autoscaling config group and you need to create a new alarm to scale your EC2 instances in response to heave web traffic. You decide to base your scaling group off an elastic load balancer metric. Which of the below would be the best metric to base this on?

  • SureQueueLength (Ans)
  • HTTPCode_BackEnd_3XX
  • HTTPCode_BackEnd_4XX
  • HTTPCode_BackEnd_5XX

You are using ElastiCache to cache your web application. The caching seems be running slower and slower and you want to diagnose the cause of this issue. You are using Memcached as your caching engine. What metric should you use to determine whether or not the amount of memory reserved for Memcached connections and other miscellaneous overhead, does not exceed 50Mb?

  • Memcached-Memory-Overhead
  • Memcached_Connections_Overhead (Ans)
  • Reddis_Connections_Overhead
  • Reddis-Memory-Overhead.

Which of the following is part of the failover process for a Multi-Availability Zone RDS instance?

  • A new DB instance is related in the standby availability zone
  • The failed RDS DB instance reboots
  • The IP of the primary DB instance is switched to the standby DB instance
  • The DNS record for the RDS endpoint is changed from primary to standby (Ans)

Your web site is hosted on 10 EC2 instances in 5 regions around the globe with 2 instances per region. How could you configure your site to maintain site availability with minimum downtime if one of the 5 regions was to lose network connectivity for an extended period of time?

  • Create an Elastic Balancer to place in front of the EC2 instances. Set an appropriate health check on each ELB.
  • Establish VPN Connections between the instances in each region. Rely on BGP to failover in the case of a region wide conncetivity outage
  • Create a Route 53 Latency Based Routing Record Set that resolves to an Elastic Load Balancer in each region. Set an appropriate health check on each ELB.
  • Create a Route 53 Lantency Based Routing Record Set that resolves to Elastic Load Balancers in each region and has the Evaluate Target Health flag set to true. (Ans)

In disaster recovery, what does RTO stand for?

  • Recovery Test Objective
  • Resilient Test Objective
  • Recovery Time Objective (Ans)
  • Resilient Training Objective

You have been hired by a large online store to help optimise their web application which is a busy online store. There are 3 webservers behind an elastic load balancer and each connects to the same RDS instance. This RDS instance started out as a small memory optimized instance but as the traffic got more and more busy the company scaled up to larger and larger instances. The current instance is a db.r3.8xlarge which is the largest RDS instance currently available and it is beginning to run out of memory. You need to find a way to further scale the web application. What should you do?

  • Increase the number of EC2 web instances so you can have even more connections to the RDS instance.
  • Advise the company to hold a sale and then contact Amazon to pre-warm the elastic load balancer.
  • Add a couple of read replica’s and adjust the application so that read only traffic is diverted to these and that only write traffic is directed to the main DB server. (Ans)
  • Advise your customer that their application has grown beyond the capabilities of AWS and should be migrated back to an premise solution.

What happens when RDS fails over from one availability zone to another?

  • You need to update the connection string in your application to point to the new RDS IP address
  • Failover is handled by AWS and the failover mechanism automatically changes the DNS record of the DB instance to point to the standby DB instance. (Ans)
  • Your application that is hosted on EC2 instances will failover automatically to the same AZ that your RDS instances have failed over to, so you do not need to do anything.
  • You need to contact AWS for advice as to how to set up your application in the new failed over availability zone.

How do you force a failover from one AZ to another using RDS?

  • Right click on the RDS instance and select “Force Failover”
  • Using the API call ” RDSForceFailover”
  • You can’t force a failover. A failover will only occur if something naturally goes wrong with the AWS estate.
  • By manually rebooting your RDS instance. (Ans)

You have a web application where the front end is hosted on EC2 and the DB is hosted on RDS in a single AZ. You notice that when back ups are taken from your RDS instance, your applications performance is severely degraded. Your boss asks you to fix the issue. What should you do.

  • Turn off backups for RDS, This will fix the performance issue immediately.
  • Upgrate your RDS instance to an instance that has better disk IO. This way the IO suspension from the back up will be “equaled out” by the increase in the new IO from the upgraded instance.
  • Create a multi-AZ RDS instance and migrate your DB to this. This way when the backups are taken, they will be taken from the secondary and not the primary. (Ans)
  • Move your RDS instance to an in house SQL which has Netbackup installed so that there is no longer a performance hit.

You have an RDS instance that is struggling to cope with the demand. What two options are best to increase performance.

  • Increase the size of the RDS insatance & enable multiple AZ’s.
  • Enable multiple AZ and add Read Replicas.
  • Increase the size of the RDS instance and add read replicas. (Ans)
  • Decrease the size of the RDS insatance but enable multiple AZ’s.

Which of the following is a reason NOT a use case for read replica’s?

  • Scaling beyond the compute or I/O capacity of a single DB Instance for read-heavy database workloads. This excess read traffic can be directed to one or more Read Replicas.
  • Providing greater redundancy via automatic failovers. (Ans)
  • Serving read traffic while the source DB Instance is unavailable. If your source DB Instance cannot take I/O request (e.g due to I/O suspension for backups or scheduled maintenance), you can direct read traffic to your Read Replica(s).
  • Business reporting or data warehousing scenarios; you may want business reporting queries to run against a Read Replia,rather than your primary, production DB Instance.

You have a multi-az enabled RDS instance and you decide to create a read replica. AWS will take a snapshot of your database. This snapshot will be from your primary database.

  • True
  • False (Ans)

What is the maximum number of read replicas can you have for your MySQL database?

  • 2
  • 3
  • 4
  • 5 (Ans)

You can have read replica’s of read replicas.

  • True (Ans)
  • False

Read Replica’s can have also have multiple AZ’s for redundancy.

  • True
  • False (Ans)

You have a fleet of EC2 instances in a private subnet and you need to securely access these via SSH. What should you implement?

  • A NAT
  • A Bastion Host/Jump Box (Ans)
  • Create a new route to your private subnet to make the subnet public.
  • A VPN concentrator.

You have created a new autoscaling group however you discover that your instances are not launching in to it. Which of the following is NOT a reason that this might be happening?

  • The associated Key Pair does not exist.
  • The security group does not exist.
  • The autoscaling config is not working correctly.
  • The autoscaling group not found.
  • Instance type specified is not supported in the AZ.
  • Instance type specified is not supported for autoscaling. (Ans)
  • You are attempting to attach and EBS block device to an instance-store AMI.

You maintain an application on AWS to provide development and test platforms for your developers. Currently both environments consist of an m1.small EC2 instance. Your developers notice performance degradation as they increase network load in the test environment.

  • Upgrade the m1.small to a large instance type (Ans)
  • Add an additional ENI to the test instance
  • Use the EBS optimized option to offload EBS traffic
  • Configure Amazon CloudWatch to provision more network bandwidth when network utilization exceeds 80%

Which of the following services does not give you root access to the underlying operating systems beneath it.

  • Elastic Map Reduce
  • ElasticBeanstalk
  • DynamoDB (Ans)
  • OpsWorks

You are about to initiate a load test on your website to ensure it can keep up with seasonal demands. Your website is behind an elastic load balancer and will receive a burst of traffic in terms of millions of requests. What should you do to prepare for this?

  • Contact Amazon and ask them to build an additional data centre.
  • Nothing, your elastic load balancer is designed to scale.
  • Contact Amazon and warn them of the test. Ask them to pre-warm the elastic load balancer. (Ans)
  • Use cloudfront and elasticache to help reduce the load.
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