Quiz2 Storage

Question 1

Your big data application is taking a lot of files from your local on-premise NFS storage and inserting them into S3. As part of the data integrity verification process, the application downloads the files right after they've been uploaded. What will happen?

S3 is eventually consistent only for DELETE or overwrite PUT

The application will receive a 404 as S3 is eventually consistent
The application will receive a 200 as S3 for new PUT is strongly consistent

Question 2

You are gathering various files from providers and plan on analyzing them once every month using Athena, which must return the query results immediately. You do not want to run a high risk of losing files and want to minimise costs. Which storage type do you recommend?

S3 General Purpose
S3 Infrequent Access
S3 One Zone Infrequent Access
S3 Glacier

Question 3

As part of your compliance as a bank, you must archive all logs created by all applications and ensure they cannot be modified or deleted for at least 7 years. Which solution should you use?

S3 General Purpose with a Bucket Policy
Glacier with a Vault Lock Policy
Glacier with a Vault Access Policy
S3 Infrequent Access with a Bucket Policy

Question 4

You are generating thumbnails in S3 from images. Images are in the images/ directory while thumbnails in the thumbnails/ directory. After running some analytics, you realized that images are rarely read and you could optimise your costs by moving them to another S3 storage tiers. What do you recommend that requires the least amount of changes?

Create two different buckets for images and thumbnails
Change the default storage class for the bucket to S3 Infrequent Access
Create a Lifecycle Rule for the entire bucket
Create a Lifecycle Rule for the images/ prefix

Question 5

In order to perform fast big data analytics, it has been recommended by your analysts in Japan to continuously copy data from your S3 bucket in us-east-1. How do you recommend doing this at a minimal cost?

Enable Cross Region Replication
Create an EC2 instance in us-east-1 and run s3 sync with a cron job
Create an EC2 instance in Japan and run s3 sync with a cron job
Use CloudFront

Question 6

Your big data application is taking a lot of files from your local on-premise NFS storage and inserting them into S3. As part of the data integrity verification process, you would like to ensure the files have been properly uploaded at minimal cost. How do you proceed?

Download the files back onto your machine and compare the MD5 hash
Compute the local ETag for each file and compare them with AWS S3's ETag
Download the files back onto your machine and compare the SHA-256 hash

Question 7

Your application plans to have 15,000 reads and writes per second to S3 from thousands of device ids. Which naming convention do you recommend?

you get about 3k reads per second per prefix, so using the device-id will help having many prefixes and parallelize your writes

<device-id>/yyyy-mm-dd/....
yyyy-mm-dd/<device-id>/....
mm-dd-yyyy/<device-id>/....
dd-mm-yyyy/<device-id>/....

Question 8

You are looking to have your files encrypted in S3 and do not want to manage the encryption yourself. You would like to have control over the encryption keys and ensure they're securely stored in AWS. What encryption do you recommend?

SSE-C
SSE-KMS
SSE-S3
Client Side Encryption
TLS encryption

Question 9

Your website is deployed and sources its images from an S3 bucket. Everything works fine on the internet, but when you start the website locally to do some development, the images are not getting loaded. What's the problem?

S3 Bucket Policies
S3 CORS
S3 ACLs
S3 Encryption

Question 10

What's the maximum number of fields that can make a primary key in DynamoDB?

partition key + sort key

1
2
3
4

Question 11

What's the maximum size of a row in DynamoDB ?

1KB
400KB
1MB
400MB

Question 12

You are writing item of 8 KB in size at the rate of 12 per seconds. What WCU do you need?

8 * 12

12
24
48
96

Question 13

You are doing strongly consistent read of 10 KB items at the rate of 10 per second. What RCU do you need?

10 KB gets rounded to 12 KB, divided by 4KB = 3, times 10 per second = 30

100
30
20
25

Question 14

You are doing 12 eventually consistent reads per second, and each item has a size of 16 KB. What RCU do you need?

we can do 2 eventually consistent reads per seconds for items of 4 KB with 1 RCU

(12/2)*(16/4)=24

192
48
24
12

Question 15

We are getting a ProvisionedThroughputExceededExceptions but after checking the metrics, we see we haven't exceeded the total RCU we had provisioned. What happened?

remember RCU and WCU are spread across all partitions

The metrics are slow to update
We have a hot partition / hot key
There's a bug in the code

Question 16

You are about to enter the Christmas sale and you know a few items in your website are very popular and will be read often. Last year you had a ProvisionedThroughputExceededException. What should you do this year?

Increase the RCU to a very, very high value
Create a DAX cluster
Migrate the database away from DynamoDB to ElastiCache for the time of the sale

Question 17

You would like to react in real-time to users de-activating their account and send them an email to try to bring them back. The best way of doing it is to...

Setup a trigger with SNS
Setup CloudWatch Events cron job that triggers a Lambda function who searches for account de-activations every 5 minutes
Enable Kinesis Streams
Integrate Lambda with a DynamoDB stream

Question 18

You would like to have DynamoDB automatically delete old data for you. What should you use?

Use TTL
Use DynamoDB Streams
Use DAX
Use a Lambda function

Question 19

You are looking to improve the performance of your RDS database by caching some of the most common rows and queries. Which technology do you recommend?

Redshift
Athena
ElastiCache
EBS