SAA-C03 Certification: RDS, Aurora and ElastiCache

RDS Read Replicas vs Multi-AZ

• Up to 15 Read Replicas

• Within AZ, Cross AZ, or Cross region

• Replication is ASYNC, so reads are eventually consistent

• Replicas can be promoted to their DB

• Use-case: can be used for the report service that doesn't need to create, update, or delete records

Network Cost

• For RDS read replicas with the same region, you don't pay that fee

Multi-AZ (Disaster Recovery)

• This is not intended for scaling. It is only for adapting to disaster recovery situations

• The Read Replicas can be set as Multi-AZ for Disaster Recovery.

• To enable Multi-AZ: click "modify" for the database and enable the multi-AZ feature.

Aurora

• It is a proprietary technology from AWS

• MySQL and Postgres are both supported as Aurora DB

• 5x performance improvement over MySQL on RDS, over 3x the performance of Postgres on RDS

• Storage automatically from 10 GB to 128 TB

• Up to 15 replicas and the replication process is faster than MySQL (10ms replica lag)

• Failover is instantaneous

• Costs more than RDS (20% more)

Aurora - High Availability and Read Scaling

• 6 copies of data across 3 AZ:

  • 4 copies out of 6 needed to write

  • 3 copies out of 6 needed for reads

  • self-healing with peer-to-peer replication

  • Storage is striped across 100s of volumes

• One Aurora instance takes writes (master instance)

• Automated failover for master in less than 30 seconds

• Master + up to 15 read replicas serve read

• Support for cross-region replication

Aurora has two types of endpoints: one for writing data and one for reading data. (Writer Endpoint and Reader Endpoint)

RDS Backup

• Automated backups:

  • Daily full backup of the database

  • Transaction logs are backed up by RDS every 5 minutes

  • \=> ability to restore to any point in time (from oldest backup to 5 minutes ago)

  • 1 to 35 days of retention, set 0 to disable automated backup

• Manual DB Snapshots

• Trick: in a stopped RDS db, you will still pay for storage. If you plan on stopping it for a long time, you should snapshot and restore instead.

Aurora Backup

• Automated backup

  • 1 to 35 days (cannot be disabled)

  • point in time recovery in that timeframe

• Manual Db snapshots (same as RDS)

Restoring an RDS / Aurora backup or a snapshot creates a new database Restoring MySQL RDS database from S3

• Create a backup of your on-premises database

• Store it on S3

• Restore the backup file onto a new RDS instance running MySQL

Restoring MySQL Aurora cluster from S3

• Create a backup of your on-premises database using Percona XtraBackup

• Store the backup file on S3

• Restore the backup file onto a new Aurora cluster running MySQL

Aurora database cloning

• Create a new Aurora Db cluster from an existing one

• Faster than snapshot & restore

• Uses copy-on-write protocol

• Very fast & cost-effective

• Useful to create a staging db from a production db without impacting the production database

RDS & Aurora Security

• At-rest encryption

  • Db master & replicas encryption using AWS KMS - must be defined as a launch time

  • If the master is not encrypted, the read replicas cannot be encrypted

  • To encrypt an un-encrypted DB, go through a DB snapshot & restore it as encrypted

• In-flight encryption: TLS-ready by default, use the AWS TLS root certificates client-side

• IAM Authentication: IAM role to connect to your DB (instead of username/password)

• Security group: control network access to RDS / Aurora DB

• No SSH available except on RDS custom

• Audit Logs can be enabled and sent to CloudWatch Logs for longer retention

RDS Proxy

• Supports RDS (MySQL, PostgreSQL, MariaDB, SQL Server) and Aurora

• Reduced RDS & Aurora failover time by up 66%

• Serverless, auto-scaling, HA (multi-AZ)

• No code changes

• RDS Proxy is never publicly accessible (must be accessed from VPC)

ElastiCache

• ElastiCache is to be managed by Redis or Memcached

• Helps make your application stateless

• Using ElastiCache involves heavy application code changes