AWS Interview Questions and Answers

1.What kind of network performance parameters can you expect when you launch instances in cluster placement group?
The network performance depends on the instance type and network performance specification, if launched in a placement group you can expect up to

• 10 Gbps in a single-flow,
• 20 Gbps in multiflow i.e full duplex
• Network traffic outside the placement group will be limited to 5 Gbps(full duplex).

2.To deploy a 4 node cluster of Hadoop in AWS which instance type can be used?
First let’s understand what actually happens in a Hadoop cluster, the Hadoop cluster follows a master slave concept. The master machine processes all the data, slave machines store the data and act as data nodes. Since all the storage happens at the slave, a higher capacity hard disk would be recommended and since master does all the processing, a higher RAM and a much better CPU is required. Therefore, you can select the configuration of your machine depending on your workload. For e.g. – In this case c4.8xlarge will be preferred for master machine whereas for slave machine we can select i2.large instance. If you don’t want to deal with configuring your instance and installing hadoop cluster manually, you can straight away launch an Amazon EMR (Elastic Map Reduce) instance which automatically configures the servers for you. You dump your data to be processed in S3, EMR picks it from there, processes it, and dumps it back into S3.

3.Where do you think an AMI fits, when you are designing an architecture for a solution?
AMIs(Amazon Machine Images) are like templates of virtual machines and an instance is derived from an AMI. AWS offers pre-baked AMIs which you can choose while you are launching an instance, some AMIs are not free, therefore can be bought from the AWS Marketplace. You can also choose to create your own custom AMI which would help you save space on AWS. For example if you don’t need a set of software on your installation, you can customize your AMI to do that. This makes it cost efficient, since you are removing the unwanted things.

4.How do you choose an Availability Zone?
Let’s understand this through an example, consider there’s a company which has user base in India as well as in the US.
Let us see how we will choose the region for this use case :
So, with reference to the above figure the regions to choose between are, Mumbai and North Virginia. Now let us first compare the pricing, you have hourly prices, which can be converted to your per month figure. Here North Virginia emerges as a winner. But, pricing cannot be the only parameter to consider. Performance should also be kept in mind hence, let’s look at latency as well. Latency basically is the time that a server takes to respond to your requests i.e the response time. North Virginia wins again!
So concluding, North Virginia should be chosen for this use case.

5.Is one Elastic IP address enough for every instance that I have running?
Depends! Every instance comes with its own private and public address. The private address is associated exclusively with the instance and is returned  to Amazon EC2 only when it is stopped or terminated. Similarly, the public address is associated exclusively with the instance until it is stopped or terminated. However, this can be replaced by the Elastic IP address, which stays with the instance as long as the user doesn’t manually detach it. But what if you are hosting multiple websites on your EC2 server, in that case you may require more than one Elastic IP address.

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