Elasticity and scalability

Question 1

What is the difference between elasticity and scalability?

Answer 1

# Elasticity is when you want met the resources of the AWS  with the traffic/work needed in current time.
# Scalability is increases the resource type through a years/months/days

Question 2

Examples of Scalability vs Elasticity for RDS and EC2:

Answer 2

# RDS:
  - Elasticity: RDS can do this, but AURORA can with serverless
  - Scalability: Modify instance type
# EC2:
  - Elasticity: Add and remove EC2`s
  - Scalability: Modify instance type EC2

Question 3

What are RDS Multi-AZ Failover?

Answer 3

Is not for scalability is for failover, Backups and restore are taken from the secondary multi-az instance, force a failover from one AZ to another by rebooting your instance.

Question 4

What are maximum read replicas for MySQL, PostgreSQL & MariaDB?

Answer 4

5

Question 5

Can have read replicas in different regions?

Answer 5

yes

Question 6

Replication on RDS is Async or Sync?

Answer 6

Async

Question 7

What are solution for create Read Replicas without 1 minute downtime?

Answer 7

Use Multi-AZ, its gonna snapshot from secondary replica.

Question 8

Read replicas can be Multi-AZ?

Answer 8

yes

Question 9

Can snapshot take from Read replicas?

Answer 9

no

Question 10

Can you have read replicas from read reaplicas?

Answer 10

yes, but will have latency for the last node.

Question 11

What is the metric to look on RDS read replica?

Answer 11

REPLICA LAG, key to see latency to create read replica

Question 12

Why read replica is not available?

Answer 12

Because you need turn on automate backups

Question 13

How to know rds engine running?

Answer 13

On console engine, or awscli rds describe-db-instances –region.

Question 14

You need Multi availability on elasticache, what to use?

Answer 14

Redis because can run Master/ slave and Multi-AZ

Question 15

What are aurora flavours?

Answer 15

Aurora and Aurora serveless

Question 16

What is aurora redundancy?

Answer 16

Is two copies of your data is contained in 3 separate availability zones wit a total of 6 copies

Question 17

What are aurora self healing?

Answer 17

Data blocks and disks are continuously scanned ofr erros and repaired automatically.

Question 18

Aurora is 100% cpu utilization what can do?

Answer 18

If write is causing, then scale up (increase instance), if is read then scale out(raise number instances read replicas)

Question 19

When create encrypted aurora whats happens next?

Answer 19

For read replicas, the encryption is turned on by deafult.

Question 20

How failover work on Aurora?

Answer 20

The lower the tiers will be promoted.

Question 21

How Cross region replica works?

Answer 21

Creating a new region replica, will create an Aurora cluster on that region, if the replications is stoped, have to set up again. Recommended to user multi-az to ensure high availability.

Question 22

What causes for instances not launching in to Autoscaling groups?

Answer 22

# Associated Key pair, Security groups, Autoscaling group does not exist.
# Autoscaling config is not working.
# Invalid EBS device mapping
# AZ is no longer suported
# No acess to autoscaling
# Attmepting to attach an EBS block device to an instance-store AMI