DynamoDB COPY

Question 1

How is DynamoDB replicated?

Answer 1

By default, DynamoDB is fully managed and replicated across 3 Availability Zones.

Question 2

How do you enable Event Driven programming in DynamoDB?

Answer 2

Use DynamoDB Streams

Question 3

What is the max size of an item/row in DynamoDB?

Answer 3

400KB

Question 4

What data types are supported in DynamoDB?

Answer 4

• Scalar Types: String, Number, Binary, Boolean, Null
• Document Types: Map, List
• Set Types: String Set, Binary Set, Number Set

Question 5

What is your first option for a primary key?

Answer 5

A Unique Hash Key / Partition Key

Question 6

What is your second option for a primary key?

Answer 6

A combination of partition key and a sort key

Question 7

What is the sort key also known as?

Answer 7

Range key

Question 8

What is RCU?

Answer 8

Read Capacity Units: throughput for reads

Question 9

What is WCU?

Answer 9

Write Capacity Units: throughput for writes

Question 10

Why would you get a “ProvisionedThroughputException”?

Answer 10

If you have temporarily exceeded your throughput limit and used all of the available burst credits.

Question 11

What should you do if you get a “ ProvisionedThroughputException”?

Answer 11

Use an exponential backoff

Question 12

Why would you get a “ProvisionedThroughputExceeded Exception”?

Answer 12

Hot keys, too many requests to the same partition or very large items exceeding the WCU/RCU.

Question 13

What can be done to resolve a “ProvisionedThroughputExceeded Exception”?

Answer 13

• Exponential backoff
• Distributed partition keys
• Dynamo Accelerator (DAX)

Question 14

What can you do to prevent ProvisionedThroughputExceeded Exceptions

Answer 14

Use Auto Scaling to increase WCU/RCU depending on activity

Question 15

What command will write to Dynamo

Answer 15

PutItem

Question 16

What command will update an item

Answer 16

UpdateItem

Question 17

How do you deal with concurrency with regards to writes?

Answer 17

Use Conditional Writes

Question 18

How do you remove from Dynamo

Answer 18

DeleteItem

Question 19

How do you do batch writes in Dynamo?

Answer 19

BatchWriteItem

Question 20

How many items can you write/delete in one PutItem/DeleteItem call for batches?

Answer 20

25

Question 21

What is the item size limit in a batch?

Answer 21

400KB

Question 22

What is the data limit that can be written in one Batch call?

Answer 22

16MB

Question 23

What happens when a batch items fails?

Answer 23

It is up to me to retry

Question 24

How can you query in Dynamo?

Answer 24

• Query on exact partitionKey

- Optional Sort Key (=, , >=, BETWEEN, BEGIN)

Question 25

What does a query return?

Answer 25

Up to 1MB of data with a limit if specified

Question 26

What is LSI in Dynamo?

Answer 26

Local Secondary Index, which is an alternate range key for your table

Question 27

How many LSI can you have per table?

Answer 27

Up to 5

Question 28

What does the sort key consist of?

Answer 28

One scalar attribute (String, Number, Binary)

Question 29

When do you declare an LSI?

Answer 29

At table creation stage

Question 30

What is a GSI?

Answer 30

Global Secondary Index which is a partition key and an optional sort key, resulting in a new table that we can assign attributes to

Question 31

What can go in a DynamoDB Stream?

Answer 31

Most changes like Create/Update/Delete

Question 32

What can read a DynamoDB Stream?

Answer 32

Lambda

Question 33

What is the data retention in DynamoDB Streams

Answer 33

24 hours

Question 34

How do you calculate WCU?

Answer 34

One write request unit represents one write for an item up to 1 KB in size. If we write 10 2KB items per second, we need 20WCU (10 x 2)

Question 35

What about items larger than 1KB?

Answer 35

More WCUs are used

- If we write 6 4.5KB items per second, we need 30WCUs (6 x 5: 4.5 gets rounded up.)

Question 36

How do you calculate RCU?

Answer 36

One read request unit represents one strongly consistent read request, or two eventually consistent read requests, for an item up to 4 KB in size.