DynamoDB

Question 1

How many facilities in a region is DynamoDB replicated

Answer 1

3

Question 2

Eventual Consistent Reads vs. Strongly

Answer 2

Eventual (Default) consistency is usually reached in under 1 second and has the best performance. Strongly requires that the data has been completely written prior to the read.

Question 3

What components are part of DynamoDB

Answer 3

Tables, Items (think rows), Attributes (think column of data in a row)

Question 4

Type of primary key that is a single attribute (think unique id) Partition key a.k.a Hash key

Answer 4

Single Attribute

Question 5

Type of primary key that composed of two attributes

Answer 5

Composite - Partition Key and Sort Key (Hash and Range)

Question 6

What does DD use to determine the physical location where the data is stored

Answer 6

Partition Key - used as an input to an internal hash function to determine location

Question 7

How are multliple items with the same Partition Key stored together

Answer 7

Using a different sort key. For example same userid creating multiple posts to a forum.

Question 8

What type of Index can only be created when creating the table, cannot be removed or modified, and has the SAME partition key, different sort key.

Answer 8

Local Secondary Index

Question 9

What type of index has a different partition key and different sort key and can be created at any time

Answer 9

Global Secondary Index

Question 10

What is more efficient to use, Scan or Query

Answer 10

Query, since it find items in a table using only primary key attribute values.

Question 11

What are DynamoDB streams used for?

Answer 11

To capture any kind of modification and then take certain action on those changes

Question 12

What changes are captured by DynamoDB Streams during an update?

Answer 12

The before and after image of any attributes that were modified in the item

Question 13

What changes are captured by DynamoDB Streams during an item delete from a table?

Answer 13

An image of the complete item before it was deleted

Question 14

What is the lifetime of a Stream

Answer 14

24 hours and then the data is subject to trimming (removal) at any given time

Question 15

How can you make a Scan operation more efficient?

Answer 15

Use the ProjectionExpression parameter which is like a filter

Question 16

You have an application that requires to read 5 items at 10KB/sec using eventual consistency. What do you set the read throughput to?

Answer 16

Round 10 up the nearest multiple of 4, so 12. Then divide 12/4 = 3. Then multiple the items by rate/per sec, so 3 x 5 = 15. For eventual consistency /2 so = 7.5 round up to 8.

Question 17

How to calculate the Write throughput?

Answer 17

Just multiply the numbers.

Question 18

Why might you receive the 400 HTTP status code of ProvisionedThroughputExceededException

Answer 18

You have exceeded your maximum allow provisioned throughput for a table for one more global secondary indexes

Question 19

Steps to authenticate with an identity provider

Answer 19

1. User authenticates with FB, 2. Token is passed, 3. You code calls AssumeRoleWithWebIdentity API and provides the providers token and specifies the ARN for the IAM role, 4. The app is now authenticated between 15min - 1 hour, 1 hour is default.

Question 20

What is special about Conditional Writes

Answer 20

They are idempotent

Question 21

What are Atomic Counters?

Answer 21

The are non-idempotent updates where you use the “UpdateItem” operation to increment or decrement the value of an existing attribute without interfering with other write requests. I.E. website hit counter

Question 22

When would you use the BatchGetItem call?

Answer 22

When you need to get multiple items at once.

Question 23

Limits of a single BatchGetItem request.

Answer 23

Can retrieve up to 1MB data containing up to 100 items. A single request can also contain items from multiple tables

Question 24

What limit of DynamoDB can be increased by a request to AWS?

Answer 24

Provisioned throughput limits and Table Size (initial limit of 256 tables per regions)