Databases (DynamoDb, RDS)

Question 1

What type of DB is Dynamo Db

Answer 1

No SQL db

Question 2

What are key features of Dynamo DB

Answer 2

DNAMO
- Distributed across multiple servers
- NoSQL (semi structured / unstructured data)
- Adapts provisioning (on demand or provisioned capacity)
- Managed Service (hardware, config, scaling, backup etc)
- Out of the box encryption (in transit and at rest)

Question 3

What are key value pairs in Dynamo DB

Answer 3

data structure used to store and retrieve data

Question 4

What is a sort key in Dynamo Db

Answer 4

organizes and orders items within the partition of a table (like a label / category)

Question 5

Which has better performance scanning or querying Dynamo db

Answer 5

Query has better performance than scanning

Querying can be efficient with partition key and sort key

Scanning should be avoided because it is slow and more expensive

Question 6

When would you use provisioned Dynamo DB vs on demand Dynamo DB

Answer 6

Provisioned is for predictable workloads with known read and write patterns

On demand capacity is for flexible, pay as you go pricing without the need to forecast usage

Question 7

How do we provision and pay for a Dynamo Db table?

Answer 7

1. Provisioned Dynamo DB table
   - Expect 1 read per second can scale up or down by 2
2. On demand Dynamo DB table
   - spins up, answers request and turns off

Question 8

Describe a real life use case for Dynamo DB

Answer 8

Netflix uses DynamoDB to manage customer meta data, preferences and session info because of its scalability, low latency, and high availability

• Ability to handle massive volumes of data is well-suited to the dynamic and high demand of Netflix
• Flexible data storage and retrieval of various types of customer data enables personalization and customization of user experiences.

Question 9

What is RDS

Answer 9

Is the service that RUNS the database engine ie., oracle, sql

RDS is the database admin

Question 10

What is Aurora?

Answer 10

Aurora is a db engine that can be managed with RDS

It is cloud native

Question 11

Why would you want a Aurora Single Master

Answer 11

If you have a simple app that doesn’t need complex data distribution or multiple masters

It has ONE ‘master’ database that handles all read and write requests

It’s like a central librarian managing all books and can make changes to them

Question 12

Why would you want Aurora Multi Master

Answer 12

If you have a globally distributed or highly responsive app

You will have multiple ‘masters’ capable of reading and writing at the same time

It’s like having multiple librarians who can check out and update books independently

Question 13

Why do you need Aurora Multiple Read Replicas

Answer 13

create copies of your database for reading data, making ur app faster because you serve customers in different locations

Question 14

Why would you need Aurora Serverless

Answer 14

• pay as you go
• auto scales based on demand

ideal for unpredictable apps

Question 15

Where does elasticache fit in the architecture?

Answer 15

Elasticache sits between apps and dbs

ie., ec2 elasticache rds

It is a managed service you can used with caching engines such as REDIS or MEMCACHED

Question 16

Name the 2 main types of keys used in Dynamo DB

Answer 16

Partition Key (Hash Key)
Sort Key (Range Key)

Question 17

Elasticache is a managed service that you can use with which 2 caching engines..

Answer 17

REDIS
MEMCACHED

Question 18

What does RDS stand for?

Answer 18

Relational Database Service

Question 19

Why is RDS useful?

Answer 19

RDS makes it easier for users to run, manage and scale relational databases without the overhead of traditional database administration tasks

Question 20

How do you identify and analyze slow performing SQL queries in your RDS database?

Answer 20

Enable slow log query feature

Question 21

What does TDE stand for?

Answer 21

Transparent Data Encryption

Question 22

What do you use Transparent Data Encryption (TDE) for?

Answer 22

Use Tranparent Data Encryption (TDE) to encrypt data at rest which protects the data

Question 23

What is Systems Manager param store used for?

Answer 23

secure way to store and manage configuration data, secrets and other params

Question 24

What is Systems Manager param store used for in RDS?

Answer 24

securley manages and stores configuration data and secrets

such as database credentials and other sensitive information, that can be securely retrieved by applications

Question 25

What is Systems Manager param store used for?

Answer 25

Systems Manager param store allows you to securely store and manage configuration data, secrets and other params

Question 26

Name the RDS database engine that was created by AWS and is entirely cloud native?

Answer 26

Aurora

Question 27

Name the RDS storage that is a good option for a broad range of use cases such as providing single-digit millisecond latencies and cost-effective storage

Answer 27

General-purpose SSD

Question 28

Which has more ElastiCache features. Redis or Memcached?

Answer 28

Redis has more features than Memcached

Question 29

What is a projection expression?

Answer 29

It is a String that identifies the attributes you want when you perform a getItem, query or scan to read data from a table

Example:
aws dynamodb get-item \
–table-name ProductCatalog \
–key file://key.json \
–projection-expression “Description, RelatedItems[0], ProductReviews.FiveStar”

This projection expression retrieves a top-level scalar attribute (Description), the first element in a list (RelatedItems[0]), and a list nested within a map (ProductReviews.FiveStar).

Question 30

When do you use Redis Elasticache vs Dynamo DB Accelerator (DAX)?

Answer 30

Use Redis Elasticache when you need flexible data storage and advanced caching needs such as data manipulation

Use DAX for improved read performance and reduced DynamoDB read traffic.

Question 31

What is a global secondary index in dynamo db?

Answer 31

a global secondary index allows you to query the table using alternate attributes as partition keys and sort keys which improves query performance

Question 32

There is an e-commerce platform where the primary table stores information about products, including attributes such as ProductID (primary key), Name, Price, Category, and Availability.

You want to be able to quickly query products from a given category

What could you add to implement this?

Answer 32

Add a global secondary index on the Category column

Ie.,
aws dynamodb update-table \
..
..
–global-secondary-index-updates \
“[{
"Create": {
"IndexName": "YourGSIName",
….

Question 33

What is a partition key in dynamo db?

Answer 33

you specify the partition key attribute to distribute data evenly across partitions

It acts as input to the hash function, determining the partition where the item will be stored

Question 34

What are global tables in dynamo db?

Answer 34

allow you to create tables that are automatically replicated across multiple AWS Regions, providing a highly available and durable solution for globally distributed applications

low-latency access to data for your globally distributed application, with high availability and disaster recovery capabilities.

Global Tables help you maintain data consistency across different regions and provide a reliable and scalable solution for applications that require global data access without compromising on performance or availability.

Question 35

Give 3 examples of when you might want to change the read capacity in dynamo db?

Answer 35

to manage fluctuating traffic patterns
optimize performance
reduce costs

Question 36

Why would your Dynamo DB app throw a Throttling error?

Answer 36

the provisioned throughput capacity for a table or an index is exceeded

Question 37

What is write around cache using Dynamo DB DAX what is the benefit?

Answer 37

directly writes data to DynamoDB so cache data is always up to date

Question 38

What is write through cache using Dynamo DB DAX and what is the benefit

Answer 38

Write-through cache with DynamoDB DAX writes data to the cache first, improving read performance by making frequently accessed data readily available.

Question 39

What is use side cache using redis along with Dynamo DB and the benefit

Answer 39

Using Redis as a side cache with DynamoDB involves storing frequently accessed data in Redis for faster retrieval, leading to improved application performance and reduced latency.

Question 40

What is write through cache using Redis along with Dynamo DB and its benefit

Answer 40

Write-through cache with Redis and DynamoDB means writing data to Redis first and then to DynamoDB, leading to improved read performance as frequently accessed data is readily available in both the cache and the primary data store.

Question 41

what does it mean to use global secondary index with projected attributes in aws?

Answer 41

allows you to specify which attributes from the main table should be copied to the index.

Question 42

Is separating the Lambda handler from the core logic is generally considered a best practice

Answer 42

Yes

Question 43

What happens if you enable dynamo db triggers?

Answer 43

you are configuring your DynamoDB table to automatically invoke a specified AWS Lambda function or an Amazon Kinesis Data Stream when certain events occur on the table. These events are typically changes to the data within the table, such as inserts, updates, or deletions

Question 44

What happens if you enable dynamo db streams?

Answer 44

Enabling DynamoDB Streams allows you to capture and track changes to items in a DynamoDB table in real time. You can use this feature to trigger actions, process data, and integrate with other AWS services, creating powerful, event-driven applications.

Question 45

What would you use to schedule a Lambda function to run on a regular basis?

Answer 45

WS CloudWatch Events or AWS EventBridge to create a scheduled event that triggers the Lambda function

Question 46

Name the 2 types of Dynamo DB read operations?

Answer 46

eventually consistent reads
strongly consistent reads

Question 47

When do you use strongly consistent reads instead of eventually consistent reads

Answer 47

Use strongly consistent reads in DynamoDB when you need the most recent data for critical operations

Use eventually consistent reads when slightly outdated data is acceptable for non-critical operations