DynamoDB

Question 1

Where is DynamoDB data stored?

Answer 1

On SSD storage

Question 2

How does Dynamo DB provide data redundancy?

Answer 2

Data in DynamoDB is spread across 3 geographically distinct data centers

Question 3

What is the data consistency model for DynamoDB?

Answer 3

Eventually Consistent Reads by Default

Strongly Consistent Reads as an option

Question 4

Roughly when are Eventually Consistent Reads consistent?

Answer 4

Data consistency is usually reached within 1 second

Question 5

What are Strongly Consistent Reads?

Answer 5

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

Question 6

What is AWS DAX?

Answer 6

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

Question 7

What is the performance improvement offered by AWS DAX?

Answer 7

10x performance improvement over DB standalone

Reduces request time from milliseconds to microseconds

Question 8

Can AWS DAX also provide write speedup?

Answer 8

Yes, it is a write-through cache

Question 9

What does DynamoDB Transactions assist with?

Answer 9

Atomic operations

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

Question 10

How does using DynamoDB Transactions affect read/write capacity?

Answer 10

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

Question 11

What is DynamoDB On-Demand Capacity?

Answer 11

Pay-per-request pricing

Question 12

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

Answer 12

There is none!

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

25 items or 4MB of data

Question 16

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

Answer 16

There is zero impact on table performance

Question 17

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

Answer 17

There is zero impact on table availability

Question 18

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

Answer 18

Data is consistent within seconds

Question 19

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

Answer 19

Data is retained until deleted

Question 20

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

Answer 20

Yes

Question 21

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

Answer 21

No

Question 22

What does PITR stand for?

Answer 22

Point-In-Time Recovery

Question 23

What is the purpose of DynamoDB PITR?

Answer 23

To protect against accidental writes and deletes

Question 24

How far back can you restore using PITR?

Answer 24

Restore to any point in the last 35 days

Question 25

How is DynamoDB backup data stored?

Answer 25

DynamoDB keeps **incremental backups** of your data

Question 26

Is DynamoDB PITR enabled by default?

Answer 26

**No**

Question 27

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

Answer 27

Typically **5 minutes** in the past

Question 28

What is a **DynamoDB Stream?**

Answer 28

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

Question 29

How long is info stored in DynamoDB Stream?

Answer 29

Info is stored for **24 hours**

Question 30

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

Answer 30

Combine **Streams** with **AWS Lambda Functions**

Question 31

What does **DMS** stand for?

Answer 31

**D**atabase **M**igration **S**ervice

Question 32

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

Answer 32

* 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

Question 33

How is data in DynamoDB stored?

Answer 33

It is stored **in JSON Format**

Question 34

What is the maximum allowed item size in DynamoDB?

Answer 34

The _key and value combined_ can be at most **400KB**