DynamoDB

Question 1

What AWS service provides a serverless, NoSQL database ideal for modern application development, with no cold starts, version upgrades, maintenance windows, patching, or downtime?

Answer 1

DynamoDB

Question 2

What is the value of a Write Capacity Unit (WCU) in AWS DynamoDB?

Answer 2

One WCU allows for one write per second for an item up to 1KB (rounds to nearest whole)

Question 3

What is the value of a Read Capacity Unit (RCU) in AWS DynamoDB?

Answer 3

One RCU allows for one strongly consistent read operation per second, or two eventually consistent read operations per second for an item up to 4KB (rounds to nearest whole)

Question 4

Which DynamoDB feature allows multiple application workers to scan segments of a table or secondary index in parallel?

Answer 4

Parallel Scan

Question 5

What actions can be taken to improve application performance when interacting with a DynamoDB table?

Answer 5

• Use queries instead of scans
• Use parallel scans (if have to)

Question 6

What does the following AWS CLI command do for DynamoDB?

aws dynamodb create-table \ --table-name Customers \ --attribute-definitions \ AttributeName=ID,AttributeType=N \ AttributeName=Name,AttributeType=S \ --key-schema \ AttributeName=ID,KeyType=HASH \ AttributeName=Name,KeyType=RANGE \ --provisioned-throughput \ ReadCapacityUnits=10,WriteCapacityUnits=5

Answer 6

Creates a Customers table with ID (number) as the partition key and Name (string) as the sort key, along with provisioned throughput of 10 RCUs and 5 WCUs

Question 7

What DynamoDB feature allows you to retrieve only specific attributes of an item?

Answer 7

Projection Expression

Question 8

Which DynamoDB feature can prevent the creation of an item if it already exists or inhibit updates based on a specific condition?

Answer 8

Conditional Expressions

Question 9

What parameter should be included in an AWS DynamoDB query to indicate the total read capacity consumed?

Answer 9

ReturnConsumedCapacity: TOTAL

Question 10

What property ensures that the most up-to-date data is returned when retrieving an item from AWS DynamoDB?

Answer 10

ConsistentRead = true during the GetItem operation

Question 11

What AWS DynamoDB operation retrieves attributes of one or more items from one or more tables and allows multiple Partition Key values in a single request?

Answer 11

BatchGetItem

Question 12

When querying AWS DynamoDB with Conditional Expressions, what parameters are required?”

Answer 12

• key condition expression (a string determining items to read)
• partition key name and value

Question 13

What AWS DynamoDB feature can be used to create backups of your tables?

Answer 13

On-demand Backup

Question 14

Which AWS DynamoDB operation allows grouping multiple actions into a single all-or-nothing transaction?

Answer 14

TransactWriteItems

Question 15

Given the requirements of reading 60 items per second (6KB each) and writing 80 items per second (1.5KB each), how do you calculate the required RCUs and WCUs for AWS DynamoDB table?

Answer 15

To calculate RCU:
1. Item size / RCU value = 6 KB / 4 KB = 1.5 round to nearest whole = 2 RCU per item
2. Reads per second * RCU per item = 60*2 = 120 RCU

To calculate WCU:
1. Item size / WCU value = 1.5 KB / 1 KB = 1.5 round to nearest whole = 2 WCU per item
2. Writes per second * WCU per item = 80 * 2 = 160 WCU

Question 16

How does DynamoDB Accelerator (DAX) handle strongly consistent reads with AWS DynamoDB?

Answer 16

For strongly consistent read requests, the DAX cluster passes all requests to DynamoDB without caching

Question 17

What is an efficient way to delete all data from DynamoDB table with minimal costs?

Answer 17

Delete the table and then re-create it using the DeleteTable operation

Question 18

How can you prevent write throttling when using a Global Secondary Index (GSI) in Amazon DynamoDB?

Answer 18

Ensure the provisioned write capacity of the GSI is equal to or greater than that of the base table, as updates write to both the table and the GSI