High Availability

Question 1

EC2

Scalability and Elasticity

Answer 1

Scalability
* Increase Instance Size as required, using reserved instances

Elasticity
* Increase the number of EC2 instances, based on autoscaling

Question 2

DynamoDB

Scalability and Elasticity

Answer 2

Scalability 
    * Unlimited amount of storage
Elasticity
    * Increase additional IOPS for additional spikes in traffic
    * Decrease that IOPS after the spike

Question 3

RDS

Scalability and Elasticity

Answer 3

Scalability

* Increase Instance Size as required.
    * from small to medium
* There is a small downtime, do it during maintenance window

Elasticity
* Can’t scale RDS based on demand

Question 4

Aurora

Scalability and Elasticity

Answer 4

Scalability
* Modify instace type, small to large
Elasticity
* Aurora Serverless

Question 5

Multi-AZ

Answer 5

• Used for Failover
• Having a synchronized copy of your Primary DB in another AZ
• It gets the endpoint and points to your other AZ

Question 6

Multi-AZ for SQL Server

Answer 6

• Engine uses synchronous logical replication

* It uses SQL Server-native Mirroring technology

Question 7

Multi-AZ for MySQL, Oracle, and PostgreSQL

Answer 7

• Engine uses synchronous physical replication

Question 8

You are doing a backup and restore, it’s affecting your production database, how can you avoid that?

Answer 8

• By enabling Multi-AZ:

* Backups and restores are taken from secondary DB which avoids I/O suspension to the primary

Question 9

Read Replicas

Answer 9

It’s a read-only database.

Question 10

When would you use Read Replicas?

Answer 10

• Scaling beyond the compute or I/O capacity of a single DB instance for read heavy workloads.
• Serving read traffic while the source DB Instance is unavailable.
• Business reporting or data warehousing scenarios:
  
  • Run your BI queries against Read Replicas, rather than primary DB Instance
  • Or use redshift to run these queries

Question 11

What happens when you create a new Read Replica?

Answer 11

• AWS takes a snapshot of your db
  
  • Multi-AZ enabled: NO downtime
  • MUlti-AZ not enabled: Downtime
• RDS manages endpoints and all

Question 12

True or False

You can have read replicas in different Regions for all engines

Answer 12

True

Question 13

True or False

Read Replicas cannot be multi-AZ

Answer 13

False - Read Replicas can be multi-AZ

Question 14

What is a key metric to look for using Read Replicas?

Answer 14

REPLICA LAG

The higher, the worst

Question 15

When is a good use case for promoting read replicas into its own DB instance?

Answer 15

• When you want to test, develop, run BI queries on your DB

* It’s like cloning your DB instance.

Question 16

How do you simulate a failover?

Answer 16

Reboot the DB so it does the failover.

Question 17

What are the steps to encrypt RDS Instances?

Answer 17

1. Take a snapshot of existing RDS instance
2. Copy the snapshot to the same/different region.
3. Encrypt the copy during the copy process
4. Restore the snap

Question 18

Sharing Encrypted RDS Snapshots between accounts

Answer 18

1. Create a CUSTOM KMS Encryption key.
2. Create an RDS snapshot using the custom key
3. Share the CUSTOM AWS KMS encryption key that was used to encrypt the snapchot
4. Use the Console, CLI, or Amazon RDS API to share the encrypted snapshot with the other account.

Question 19

What happens when Aurora is at 100% CPU Utilization?

Writes causing issue.

Answer 19

Scale Up → Increase instance size

Question 20

What happens when Aurora is at 100% CPU Utilization?

Reads causing issue.

Answer 20

Scale Out → Add more read replicas

Question 21

aws rds describe-db-instances –region

What does this command do?

Answer 21

See what version you are using, and all the description for the instance that you are using.

Question 22

Which Services have Maintenance Windows?

RERDND

Answer 22

• RDS
• Elasticache
• Redshift
• DynamoDB DAX
• Neptune
• Amazon DocumentDB

Question 23

Services without maintenance windows:

Answer 23

• EC2
• Lambda
• QLDB

Question 24

Which engine of ElastiCache support Multi-AZ?

Answer 24

Redis - Master/Slave replication

- Memcached does not support Multi-AZ

Question 25

_____ ______ _______ is the number of times that your edge locations are able to serve content back to your user without having to go back to the origin. The more requests from edge locations, the better.

Answer 25

Cache Hit Rations (CloudFront)

Question 26

Where can I visualize the Cache Hit Ratio?

Answer 26

On the CloudFront Console.

Question 27

To increase your cache hit ratio, you can configure your origin to add a Cache-Control: max-age directive to your objects, and specify the longest practical value for a max-age. So, the shorter the cache duration, the more frequently CloudFront forwards another request to your origin to determine whether the object has changed, and, if so, to get the latest version.

Answer 27

Specifying how long CloudFront Caches your objects. (TTL)

Question 28

What is important to make sure of when Caching based on Query String Parameters?

Answer 28

Make sure that you do consistent naming convention across your application for variables using query string parameters. http: //www.example.com?id=a1 http: //www.example.com?id=A1 http: //www.example.com?Id=a1 http: //www.example.com?ID=a1 These would generate 4 different requests to the origin, because the parameter is case sensitive.

Question 29

Caching based on Cookie Values, how should you configure?

Answer 29

- Create separate cache behaviors for static and dynamic content - Configure CloudFront to forward cookies to your origin only for dynamic content.

Question 30

6 ways to improve CloudFront Cache Hit Ratio:

Answer 30

- Specifying how long CloudFront Caches your objects - Caching based on Query String Parameters - Caching based on Cookie Values - Caching based on Request Headers - Remove Accept-Enconding Headers when compression is not needed - Serving media content by using HTTP

Question 31

Caching based on Request Headers, how should you configure?

Answer 31

- Configure CloudFront to forward and cache based only on specified headers instead of forwarding and caching based on all headers. - Avoid caching based on request headers that have large numbers of unique values.

Question 32

How can you serve media content by using HTTP?

Answer 32

You can use CloudFront to deliver video on demand or live streaming video using any HTTP origin. Use CloudFront together with AWS Media Services.

Question 33

What does list of things may show you? * Associated key pair does not exist * Security Group does not exist * Autoscaling config is not working correctly * Austoscaling group not found * Instance type specified is not supported in the AZ * AZ is no longes supported * Invalid EBS device mapping * Autoscaling service is not enabled on your account * Attempting to attach an EBS block device to an instance-store AMI

Answer 33

The reason for my instance not launching into an autoscaling group.

Question 34

Aurora Cross Region Replicas:

Answer 34

* Creating a new cross region replica will also create a new Aurora cluster in the target region. * If replications is disrupted, you will have to set up again. * It is recommended that you select Multi-AZ deployment to ensure high availability for the target cluster.

Question 35

Aurora Encryption

Answer 35

* Turned on by default | * All read replicas will be encrypted

Question 36

Aurora Failover

Answer 36

* It is defined by tiers * The lower the Tier, higher the priority. * Tier 0 → highest priority

Question 37

Amazon ElastiCache can fulfill a number of roles. What are thee things which can be implemented using Elasticache for Redis.

Answer 37

- Sorted Sets - In Memory Data Store - Pub/Sub

Question 38

How can you implement redundancy for your RDS DB instances?

Answer 38

Redundancy = High Availability | - Using Multi-AZ Deployments