Elasticity and scalability Flashcards
What is the difference between elasticity and scalability?
# 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
Examples of Scalability vs Elasticity for RDS and EC2:
# 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
What are RDS Multi-AZ Failover?
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.
What are maximum read replicas for MySQL, PostgreSQL & MariaDB?
5
Can have read replicas in different regions?
yes
Replication on RDS is Async or Sync?
Async
What are solution for create Read Replicas without 1 minute downtime?
Use Multi-AZ, its gonna snapshot from secondary replica.
Read replicas can be Multi-AZ?
yes
Can snapshot take from Read replicas?
no
Can you have read replicas from read reaplicas?
yes, but will have latency for the last node.
What is the metric to look on RDS read replica?
REPLICA LAG, key to see latency to create read replica
Why read replica is not available?
Because you need turn on automate backups
How to know rds engine running?
On console engine, or awscli rds describe-db-instances –region.
You need Multi availability on elasticache, what to use?
Redis because can run Master/ slave and Multi-AZ
What are aurora flavours?
Aurora and Aurora serveless
What is aurora redundancy?
Is two copies of your data is contained in 3 separate availability zones wit a total of 6 copies
What are aurora self healing?
Data blocks and disks are continuously scanned ofr erros and repaired automatically.
Aurora is 100% cpu utilization what can do?
If write is causing, then scale up (increase instance), if is read then scale out(raise number instances read replicas)
When create encrypted aurora whats happens next?
For read replicas, the encryption is turned on by deafult.
How failover work on Aurora?
The lower the tiers will be promoted.
How Cross region replica works?
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.
What causes for instances not launching in to Autoscaling groups?
# 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
