DynamoDB

Question 1

Eight things about DynamoDB?

Answer 1

• Fully managed
• Multi-region
• Multi-master
• Durable
• Built-in security
• Backup and restore
• In-memory caching
• Data is stored across multiple AZs

Question 2

What are the 2 types of reads that DynamoDB provides?

Answer 2

• Strongly Consistent Reads

- Eventually Consistent Reads (Default)

Question 3

The Key Value and Document database solution for AWS

Answer 3

DynamoDB (NoSQL)

Question 4

What are the 3 components of a DynamoDB table?

Answer 4

• Keys
• Values
• Attributes

Question 5

How many partitions does a DynamoDB database start off with?

Answer 5

1

Question 6

How large can a single DynamoDB partition be? (GB)

Answer 6

10GB

Question 7

The maximum read and write capacity units for a single DynamoDB partition

Answer 7

3000 Read Capacity Units, 1000 Write Capacity Units

Question 8

These 2 components make up a composite primary key in DynamoDB

(kəmˈpɑzət)

Answer 8

Partition Key & Sort Key

Question 9

In Dynamo DB, When using a simple primary key how many items can have the same partition key?

Answer 9

1

Question 10

In Dynamo DB, What additional key component makes a primary key composite?

Answer 10

Sort key

• (The combination of the partition and the sort has to be unique) There is a secret internal hash function that decides which partition to write data
• New data is added into a partition with similar data, Eg. a category
• Partition Key: Category
• Sort Key: Name

Question 11

In Dynamo DB, with composite keys multiple items share the same partition key (as long as their sort keys are different)
True or False

Answer 11

True.

• Partition Key: Country
• Sort Key: Citiy

Partition A:
VE - CCS
VE - MCBO
Partition B:
CL - STGO
CL - CONCE

Question 12

In Dynamo DB, The 2 methods of retrieving items from a DynamoDB table

Answer 12

Query & Scan

Question 13

In Dynamo DB, By default what item attributes does a query return?

Answer 13

All attributes

Question 14

This DynamoDB item retrieval method finds items based on primary key values.

Answer 14

Query

Question 15

This DynamoDB item retrieval method checks all items, then returns one of more item using filters

Answer 15

Scan

• Scans are one of the most expensive ways to access data in DynamoDB
• Scans can be Slow

Question 16

In Dynamo DB, which method do you have to avoid because it retrieves everything.
It’s much less efficient than running the other one

Answer 16

Scan

• Scans are one of the most expensive ways to access data in DynamoDB
• Scans can be Slow

Question 17

With DynamoDB the maximum amount of capacity your application is allowed to read or write per second from a table or index is called this. (The name of the capacity)

Read/Write capacity mode: ___

Answer 17

Provisioned Throughput Capacity
(prəˈvɪʒənd ˈθruˌpʊt kəˈpæsəti)

Provisioned

• RCUs
• WCUs

We can turn on Auto Scaling

Requests that are throttled will be dropped (data lost)

Question 18

With this DynamoDB capacity type you only pay per request - so you are only paying for what you use

Read/Write capacity mode: ___

Answer 18

On-Demand Capacity

• Provisioned capacity not applicable
• Auto Scaling not applicable

New tables with unknown workloads, unpredictable application traffic

Default upper limits for a table
40,000 RCUs
40,000 WCUs

• Since there is no hard limit On-Demand could become very expensive based on emerging scenarios

Question 19

In DynamoDB,

What are the 3 requirements for creating a Global Table?

Answer 19

• KMS CMK
• Enable Streams
• StreamViewType (What info is going to be written to the stream)KEYS_ONLY - Only the key attributes of the modified item are written to the stream.NEW_IMAGE - The entire item, as it appears after it was modified, is written to the stream.OLD_IMAGE - The entire item, as it appeared before it was modified, is written to the stream.NEW_AND_OLD_IMAGES - Both the new and the old item images of the item are written to the stream.

Question 20

How many underlying reads or writes does DynamoDB perform on every item in a transaction?

Answer 20

2

• One to prepare the transaction
• One to commit the transaction

Question 21

The 2 operations for performing transactions with DynamoDB

Answer 21

• TransacWriteItems

- TranscGetItems

Question 22

Which format must you provide your TTL value in?

Answer 22

To use TTL you must use a string which needs to be In Epoch format (Datetime represented as numbers)

(ˈipək) format

Question 23

What is TTL in DynamoDB?

Answer 23

Time To Live
- It’s great for keeping databases small and manageable because some data is deleted when it expires
Eg: Session data, Usage Patterns, Some logs

Question 24

In DynamoDB this value specifies when an item should expire/delete itself

Answer 24

Time To Live (TTL) Value

Question 25

Enabling this DynamoDB feature on a table will capture every modification to data items so you can react those changes.

Answer 25

DynamoDB Streams | - It doesn't not consume RCU

Question 26

Which of the following is true about DynamoDB streams? | There are three answers:

Answer 26

- Changes are sent in batches at a time - Changes are sent to Lambda in near real-time - It doesn't consume RCU's

Question 27

Which of the following are common errors for DynamoDB? ..Exception .. .. ...Exception

Answer 27

- ThrottlingException (ˈθrɑtəlɪŋ ɪkˈsɛpʃən) This exception might be returned if you perform control plane API operations too rapidly. (CreateTable, UpdateTable, ListTables) For tables using on-demand mode, this exception might be returned for any data plane API operation if your request rate is too high. (CRUD actions on data in a table) - ProvisionedThroughputExceededException Your request rate is too high. The AWS SDKs for DynamoDB automatically retry requests that receive this exception. Your request is eventually successful, unless your retry queue is too large to finish. Reduce the frequency of requests using Error Retries and Exponential Backoff.

Question 28

The 2 types of secondary indexes available for DynamoDB. ˈsɛkənˌdɛri Which Should you use generally?

Answer 28

- LSI - Local Secondary Index > With initial table (After creation, nothing to do) > It provides strong consistency > It can't exceed 10GB (It's per partition) > Composite keys ``` - GSI Global Secondary Index > Generally use this > Queries on the index can span all of the data across all partition > Maximum 20 per table > Eventual consistency reads ```

Question 29

What are some scenarios would be ideal to consider DAX? (sɪˈnɛrioʊz) There are two scenarios in the list

Answer 29

It is a fully managed, highly available, in-memory cache for Amazon DynamoDB 1. Apps requiring the fastest possible response time for reads > Real-time bidding, social gaming 2. Apps that read a small number of items more frequently than others

Question 30

This DynamoDB enhanced feature provides a fully managed in memory cache that runs in a cluster enhanced

Answer 30

DynamoDB Accelerator (DAX)

Question 31

What do DynamoDB Transactions let you do?

Answer 31

Query multiple tables at once and is an all-or-nothing approach

Question 32

In DynamoDB, How do you calculate RCU?

Answer 32

Strong = (KB p.item) / 4 * (desirable RCU) Eventual = ((KB p.item) / 4 * (desirable RCU)) /2

Question 33

In DynamoDB, How do you calculate WCU?

Answer 33

(KB) * Desired - round 1.5kb to 2kb - round 500bytes to 1kb

Question 34

In DynamoDB | If you don't need DAX, please consider...

Answer 34

ElastiCache | ɪˈlæstɪ-kæʃ

Question 35

In DynamoDB aws dynamodb - It returns a set of attributes for new item with given primary key - It creates a new item (If the id exists, it replaces the old element) - It edits an existing item's attributes - It returns the attributes of one or more items from one or more tables (Up tp 16mb and 100 items) - It puts or deletes multiple items in one or more tables (25 put or delete requests) - It adds a new table to your account - It modifies the provisioned throughput settings, secondary index - It Deletes a table and all of its items - A synchronous operation that atomically retrieves multiple items from one or more tables (25 objects < 4mb) - A synchronous write operation that groups up to 25 action requests - It finds items based on primary key values - It returns one or more items and items attributes by accessing every item

Answer 35

``` > get-item > put-item > update-item > batch-get-item > batch-write-item > create-table > update-table > delete-table > transact-get-items > transact-write-items > query > scan ```

Question 36

What is Dynamo DB? | What are its 13 elements?

Answer 36

- It's a key-value and document NOSQL database - Consistency types (Eventually...) - Data types (Binary, Number, String) - Tables anatomy (Items, attributes) - Partitions - Types of Primary Key (Simple, composite) - Global tables - Transactions (TransacGetItems...) - Streams (Trigger lambda functions) - Secondary indexes (GSI, LSI) - Types of operation searches (Query, Scan) - Capacity Modes (Provisioned, On-Demand) - Calculate reads and writes - DAX

Question 37

How do you reduce the frequency of failed requests to avoid ProvisionedThroughputExceeded on DynamoDB?

Answer 37

Error Retries and Exponential Backoff. The idea behind exponential backoff is to use progressively longer waits between retries for consecutive error responses. You should implement a maximum delay interval, as well as a maximum number of retries. The maximum delay interval and maximum number of retries are not necessarily fixed values, and should be set based on the operation being performed, as well as other local factors, such as network latency.

Question 38

In order to give you the ability to retrieve data from your DynamoDB tables more rapidly you need to use: Two elements in the answer

Answer 38

- Parallel Scans | - limiting the rate