RDS + Aurora + ElastiCache

Question 1

RDS

Answer 1

• Multi AZ instances can be enabled for HA
• Multi AZ provides synchronous replication (Read Replicas is asynchronous)
• Read Replicas can be setup for Multi AZ in DR
• Multi AZ ONLY supports same region
• Failover takes 1-2 minutes, only compliant with HA, not FT
• Can perform manual failover
• Read Replicas can be setup as Multi AZ for DR

Question 2

RDS Restores

Answer 2

• Creates a new RDS Instance - with a new endpoint address

- Restores are SLOW - think about RTO

Question 3

RDS Read Replicas

Answer 3

• Only supports 5 Read Replicas at once
• Enables HA
• Replicas can be promoted to Primary in DR event
• Can be created Cross Region
• Provides asynchronous replication (Multi AZ is synchronous)
• Can use for reporting without affecting primary instance
• Network cost is oncurred for traffic from one AZ to another

Question 4

RDS Encryption

Answer 4

• Supports EBS volume encryption (using KMS)
• Encryption cannot be removed once added
• If master instance is not encrypted, Read Replicas can’t either
• MySQL and Oracle support Transparent Data Encryption (TDE)

Question 5

Aurora

Answer 5

• Supports 15 replicas
• dont need to specify storage requirements
• Uses shared storage volume for master and read replicas
• Backtrack: restore data at any point of time without using backups

Question 6

Aurora Serverless

Answer 6

• Scalable: uses Aurora Capacity Units
• Can incur 0 costs if not used
• Good for infrequent, intermittent or unpredictable workloads
• Application will use ‘proxy fleets’ which automatically connect to underlying Aurora Capacity Units

Question 7

Aurora Global

Answer 7

• Allows global replication with upto 5 regions
• Cross Region Read Replicas
• 1 Primary region, with 5 secondary read-only regions

Question 8

Aurora Multi Master Writes

Answer 8

• Multiple master instances that support read and write operations
• Application can connect to one or both masters at a time
• Cluster proposes data to other master to synchronise
• Much better availability, and failover event will not disrupt traffic, as the other writer will take over

Question 9

ElastiCache

Answer 9

• in-memory database to cache data for READ HEAVY worklods with low latency requirements
• can reduce workload on DB
• can store session data
• However, requires application code changes to check for things at ElastiCache
• Support SSL in flight encryption
• DO NOT SUPPORT IAM AUTHENTICATION

Question 10

Elasticache: Memcachd

Answer 10

• Supports only simple data structures (strings)
• No replication
• Multiple nodes
• No backups
• Multi-threaded by design

Question 11

Elasticache: Redis

Answer 11

• Supports advanced structures, such as lists, sets, stored sets, bit arrays
• Supports Multi-AZ
• Replication
• Supports Backup and Restore