Most popular aws interview questions

AWS most popular interview questions

1. What type of performance can you expect from Elastic Block Storage? How do you back it up and enhance the performance?

Performance of elastic block storage varies i.e. it can go above the SLA performance level and after that drop below it. SLA provides an average disk I/O rate which can at times frustrate performance experts who yearn for reliable and consistent disk throughput on a server. Virtual AWS instances do not behave this way. One can backup EBS volumes through a graphical user interface like elasticfox or use the snapshot facility through an API call. Also, the performance can be improved by using a Linux software raid and striping across four volumes.

2. Imagine that you have an AWS application that requires 24x7 availability and can be down only for a maximum of 15 minutes. How will you ensure that the database hosted on your EBS volume is backed up?

Automated backup is the key processes here as they work in the background without requiring any manual intervention. Whenever there is a need to back up the data, AWS API and AWS CLI play a vital role in automating the process through scripts. The best way is to prepare for a timely backup of EBS of the EC2 instance. The EBS snapshot should be stored on Amazon S3 and can be used for recovery of the database instance in case of any failure or downtime. 

3. You create a Route 53 latency record set from your domain to a system in Singapore and a similar record to a machine in Oregon. When a user located in India visits your domain, to which location will he be routed to?

Assuming that the application is hosted on Amazon EC2 instance and multiple instances of the applications are deployed on different EC2 regions. The request is most likely to go to Singapore because Amazon Route 53 is based on latency and it routes the requests based on the location that is likely to give the fastest response possible.

4. Differentiate between on-demand instance and spot instance.

Spot Instances are spare unused EC2 instances which one can bid for. Once the bid exceeds the existing spot price (which changes in real-time based on demand and supply) the spot instance will be launched. If the spot price becomes more than the bid price then the instance can go away anytime and terminate within 2 minutes of notice. The best way to decide on the optimal bid price for a spot instance is to check the price history of the last 90 days that is available on the AWS console. The advantage of spot instances is that they are cost-effective and the drawback is that they can be terminated anytime. Spot instances are ideal to use when –

• There are optional nice to have tasks.
• You have flexible workloads which can be run when there is enough compute capacity.
• Tasks that require extra computing capacity to improve performance.
On-demand instances are made available whenever you require them and you need to pay for the time you use them on an hourly basis. These instances can be released when they are no longer required and do not require any upfront commitment. The availability fo these instances is guaranteed by AWS unlike spot instances.
The best practice is to launch a couple of on-demand instances which can maintain a minimum level of guaranteed compute resources for the application and add-on few spot instances whenever there is an opportunity.

5. How will you access the data on EBS in AWS ?

Elastic block storage as the name indicates provides persistent, highly available and high-performance block-level storage that can be attached to a running EC2 instance. The storage can be formatted and mounted as a file system or the raw storage can be accessed directly.