Amazon Relational Database Service (RDS)

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Useful Links:
Exam Tips:
- Most use cases, General Purpose SSD is fine.
- Have knowledge of backup retention period.
- Backups:
  - Saved to S3, where it is then replicated.
  - Automatic backups:
    - For true Point-in-Time recovery.
    - It is done using transaction logs in automatic backups.
  - Snapshots.
- Replication:
  - Replication is between master (primary) and slave (standby) node.
    - Failure of primary and standby AZs would impact service.
  - No access to slave node when the master node is working.
  - No storage replication.
- Payment methods:
  - On-demand
  - Reserved:
    - All upfront
    - Partial upfront
    - No upfront
    - Terms 1-3 yrs
- New database can be created using a snapshot.
- Read Replicas:
  - Asynchronous = Read-replicas.
  - Cannot be used for write operations.
  - Can be deployed to another AZ, or even another region.
  - Good for read intensive applications.
  - Can be addressed directly as opposed to a slave node.
  - Is a completely DB instance
  - Can have a different DB version.
  - Used globally.
  - Performance:
    - 5x direct read-replicas per DB instance.
    - Each providing an additional instance of read performance.
    - Read-replicas can have read-replicas, but lag starts to be a problem.
    - Global performance improvements.