DynamoDB

Question 1

Elasticache

Answer 1

Webservice that makes it easy to to scale an in memory cache in the cloud.

Question 2

Elasticache Case Point

Answer 2

Retrieve top daily deals. Use cache instead of of DB.

Question 3

DynmoDB

Answer 3

1) NOSQL DB single digit milisecond latency
2) Stored on SSD
3) 3 Geographically distinct locations

Question 4

2 Types of Primary Keys

Answer 4

1) Single Attribute

2) Composite

Question 5

Single Attribute

Answer 5

Partition key (also known as HashKey)

Question 6

Composite

Answer 6

Partition Key + Sort Key.

Can have the same Partition key (so they are all stored together) but different sort key.

All sorted by sort key value

Question 7

Streams

Answer 7

Captures any modification of DynamoDB Table. Can trigger Lambda functions through use of triggers. Streams must be enabled.

1) New Item - Captures Entire Image
2) Delete - Captures image of entire item
3) Update - Captures before and after image of any attribute modified

Question 8

Query

Answer 8

Find items in a table by using only the primary key.

You must provide a partition key attribute name and distinct value to search for.

Typically the most efficient search.

Sort order is Ascending by default and you can use ScanIndexForward to reverse order

Question 9

Project Expression

Answer 9

Allows you to specify what attributes to return on either Queries or Scans.

Question 10

ScanIndexForward

Answer 10

Used to change the Sort order of a Query Only. By Default queries sort are Ascending by default and you can use ScanIndexForward to reverse order.

Question 11

Scan

Answer 11

Examines every item and returns every attribute by default. Must use ProjectExpression to limit attributes.

-Optimize Scan by designing the tables to

Question 12

Index Types

Answer 12

1) Local Secondary Index

2) Global Secondary Index

Question 13

Local Secondary Index

Answer 13

• Same Partition Key
• Different Sort Key.

Can only be created during table creation. Cannot be deleted.

Supports both Eventual and Strong Consistency

Question 14

Global Secondary Index

Answer 14

• Different Partition Key
• Different Sort Key

Can be created at anytime and can be deleted.

Supports only Eventual Consistency

Question 15

Eventual Consistent Read Formula

Answer 15

(Read Size nearest 4KB/4KB) * (Items) / 2 =Eventual Consistent Read Throughput

Question 16

Eventual Consistent Reads

Answer 16

• Read 4KB

- 2 Reads per second

Question 17

Strongly Consistent Reads

Answer 17

-1 Read per second

Question 18

Strongly Consistent Read Formula

Answer 18

(Read Size nearest 4KB/4KB) * (Items) =Eventual Consistent Read Throughput

Question 19

Eventual & Strongly Consistent Write Formula

Answer 19

(KB Size) * (Items) = Write Throughput

Question 20

Web Identity Provider Process

Answer 20

1) User Autheticates with ID Provider (Such as Facebook, Google, Amazon)
2) Provider passes back a token
3) Your code calls AssumeWithWebIdentity API. Uses providers token and specifies the ARN (Amazon Resource name) for the IAM Role.
4) App can now access DynamoDB between 15min-1hr. Set to 1hr by default.

Question 21

Exceeded Throughput Error

Answer 21

400 HTTP Status code -

ProvisionedThroughputExceededException

Question 22

Conditional Writes

Answer 22

You can send multiple conditional write statements but only the 1st works. Perfect for banking.

Question 23

Atomic Counters

Answer 23

Counter that you can change unconditionally.

Use UpdateItem to increment/decrement.

Great for unimportant counters as they are not Idempotent.

Question 24

Batch Operations

Answer 24

Allows app to read multiple items/tables.

Question 25

Projected Indexes

Answer 25

Data in index is copied from table

Question 26

Security for DynamoDB

Answer 26

IAM/Fine Grained Access Control

Question 27

Pricing

Answer 27

Charged by throughput capacity

Question 28

Data Replication

Answer 28

Amazon replicates data across 3 Regions

Question 29

When should you not use DynamoDB

Answer 29

Large amount of rarely accessed data. Giant blobs are better stored in S3.

Question 30

Attribute Limitation

Answer 30

No limit of attributes within an item.

Question 31

Item Size Limit

Answer 31

400 KB including attributes/names/values

Question 32

DynamoDB Data Structure

Answer 32

Key-Value and document data structure.

Question 33

JSON Datatype supported?

Answer 33

No, however you can convert by using Document SDK

Question 34

Limit on throughput

Answer 34

No limit on throughput. Must contact sales once it gets so high.

Question 35

AutoScalling - When is it ideal

Answer 35

Ideal for predictable requests with sustained usage for minutes to hours.