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Fully Merged AWS SA Prep > DynamoDB > Flashcards

DynamoDB Flashcards

1
Q

What is AWS DynamoDB?

A

DynamoDB is a fast and flexible NoSQL DB service for all applications that need consistent, single-digit milliscond latency at any scale

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2
Q

Does DynamoDB support document data models?

A

Yes

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3
Q

Does DynamoDB support key-value data models?

A

Yes

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4
Q

Where is DynamoDB data stored?

A

On SSD storage

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5
Q

How does Dynamo DB provide data redundancy?

A

Data in DynamoDB is spread across 3 geographically distinct data centers

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6
Q

What is the data consistency model for DynamoDB?

A

Eventually Consistent Reads by Default

Strongly Consistent Reads as an option

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7
Q

Roughly when are Eventually Consistent Reads consistent?

A

Data consistency is usually reached within 1 second

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8
Q

What are Strongly Consistent Reads?

A

A strongly consistent read reflects all writes that received a successful response prior to the read.

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9
Q

What does DAX stand for?

A

DynamoDB Accelerator

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10
Q

What is AWS DAX?

A

Fully managed, highly-available in-memory cache for DynamoDB

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11
Q

What is the performance improvement offered by AWS DAX?

A

10x performance improvement over DB standalone

Reduces request time from milliseconds to microseconds

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12
Q

What does the developer need to do to manage the logic in AWS DAX?

A

Nothing. The caching logic is fully managed by AWS

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13
Q

Can AWS DAX (DynamoDB Accelerator) also provide write speedup?

A

Yes, it is a write-through cache

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14
Q

What does DynamoDB Transactions assist with?

A

Atomic operations

(Think money transfer, can’t debit one account without crediting another)

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15
Q

How does using DynamoDB Transactions affect read/write capacity?

A

Transactions does 2 underlying reads or writes of every item in the transaction, one to prepare, and one to commit.

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16
Q

What is DynamoDB On-Demand Capacity?

A

Pay-per-request pricing

17
Q

What is the minimum capacity required for DynamoDB On-Demand capacity?

A

There is none!

18
Q

What is the pricing model for DynamoDB On-Demand Capacity?

A
  • No charge for read/write while the table is idle, only for storage and backups
  • Pay more per request than with provisioned capacity
19
Q

What is the recommended use case for DynamoDB On-Demand Capacity?

A

New Product Launches, when you don’t have a sense ahead of time of how much traffic to expect

20
Q

What is the maximum amount of data on which DynamoDB Transactions can operate at any time?

A

25 items or 4MB of data

21
Q

What is the performance hit of AWS DynamoDB On-Demand Backup and Restore?

A

There is zero impact on table performance

22
Q

What is the availability hit of using DynamoDB On-Demand Backup & Restore?

A

There is zero impact on table availability

23
Q

What is the data consistency model for DynamoDB On-Demand Backup and Restore?

A

Data is consistent within seconds

24
Q

What is the data retention model for DynamoDB On-Demand Backup & Restore?

A

Data is retained until deleted

25
Q

Can you have a DynamoDB On-Demand Backup in the same region as the source table?

A

Yes

26
Q

Can you have a DynamoDB On-Demand Backup in a different region from your source table?

A

No

27
Q

What does PITR stand for?

A

Point-In-Time Recovery

28
Q

What is the purpose of DynamoDB PITR?

A

To protect against accidental writes and deletes

29
Q

How far back can you restore using PITR?

A

Restore to any point in the last 35 days

30
Q

How is DynamoDB backup data stored?

A

DynamoDB keeps incremental backups of your data

31
Q

Is DynamoDB PITR enabled by default?

A

No

32
Q

With DynamoDB PITR, how far back is the latest restorable time stamp?

A

Typically 5 minutes in the past

33
Q

What is a DynamoDB Stream?

A

A time-ordered sequence of item-level changes in a table

34
Q

How long is info stored in DynamoDB Stream?

A

Info is stored for 24 hours

35
Q

If you wanted to imitate a stored procedure functionality in Dynamo DB, how might you do it?

A

Combine Streams with AWS Lambda Functions

36
Q

What does DMS stand for?

A

Database Migration Service

37
Q

What are some of the ways you can get security in DynamoDB?

A
  • Encryption at Rest (with KMS)
  • site-to-site VPN
  • Direct Connect
  • IAM Policies & Roles (or fine-grained access)
  • mornitoring using CloudWatch and CloudTrail
  • VPC endpoints

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