aCloudGuru: Amazon DynamoDB Deep Dive

Question 1

02 Databases 101 / 03 NoSQL Database Models

What is BASE?

Answer 1

BA - Basic Availability - db appears to work most of the time

Soft state: stores don’t have to be write-consistent, nor do different replicas have to be mutually consistent all the time

Eventual consistency: stores exhibit consistency at some later point

Question 2

03 DynamoDB and Secenario Introduction / 01 DynamoDB 10,000 FT

Is DynamoDB supporting ACID?

Answer 2

Yes.

Question 3

04 Table and Item Architecture / 02 DynamoDB Items

Is there any limit for item size?

Answer 3

Yes - 400KB

Question 4

05 Accessing DynamoDB / 01 Using the AWS Management Console

What is the requirement for table uniqueness?

Answer 4

Table name must be unique per AWS account and region.

Question 5

05 Accessing DynamoDB / 01 Using the AWS Management Console

When LSI can be created?

Answer 5

Only during table creation.

Question 6

05 Accessing DynamoDB / 03 SDK Options

What type of interfaces can be used to access DynamoDB?

Answer 6

1. Low-Level Interface (HTTP)
2. Document Interface (Java/.NET/JS)
3. High-Level Interface (Object Persistence Interface) (Java/.NET)

Question 7

07 Working with Items / 02 Performance Units: RCU/WCU

How many RCUs are consumed for

• one strong consistent read
• eventually consistent read
• transactional read

assuming that we try to read 8KB item

Answer 7

• 2 RCU
• 1 RCU
• 4 RCU

Question 8

07 Working with Items / 02 Performance Units: RCU/WCU

How many WRUs will be used to write an item of 3KB for standard/transactional?

Answer 8

• Standard: 3 WCUs
• Transactional: 6WCUs

Question 9

10 Table Indexes / 02 Indexes: Part 2

3 options for projection expressions.

Answer 9

1. ALL
2. KEYS_ONLY
3. INCLUDE

Question 10

10 Table Indexes / 02 Indexes: Part 2

What is GSI?

Answer 10

Global secondary index - can have partition key different than partition key of parent table and optional sort key.

Question 11

10 Table Indexes / 02 Indexes: Part 2

What is sparse index?

Answer 11

Sparse index is an index that doesn’t contain all table elements because sort key is not present in every item.

Question 12

12 Advanced Performance and Scaling Considerations / 02 Hot and Cold Partition Imbalance

What is adaptive capacity?

Answer 12

When there is a hot partition DynamoDB can allow to have higher consumed capacity over provisioned capacity on this partition provided that other partition consume less.

Assuming that total provision capacity = 400 whereas consumed is 300, then having 4 partition the consumed capacity can be distributed as 50/50/50/150.

Question 13

12 Advanced Performance and Scaling Considerations / 02 Hot and Cold Partition Imbalance

How # partitions is calculated?

Answer 13

RCU/3000 + WCU/1000 = # Partitions

Question 14

16 Streams and Triggers / 01 Streams

What view types can be selected when managing a stream?

Answer 14

1. Keys only
2. New image
3. Old image
4. New and old image

Question 15

17 Advanced Index Usage

What are two techniques for aggregation in DynamoDB?

Answer 15

1. Selective write sharding (main process write data + shards from 2 tables, lambda launched on trigger calculates data from 2nd table and put aggregate results into it)
2. Aggregation with stream (lambda triggered by stream is writing calculated data directly into new table)