RDS
OLTP is RDS
RDS Storage Auto Scaling automatically scales storage capacity in response to growing database workloads, with zero downtime
Using AWS DMS, you can migrate Oracle relational database running in an on-premises data center to Amazon RDS without modifying the application's code
RDS Read Replica
Read replica for read operation, helps improve RDS overall performance (as reads are redirected to read replica)
Read Replica support multi-region
When you create a read replica
Amazon RDS takes a DB snapshot of your source DB instance and begins replication
If you create multiple read replicas only one snapshot is created at the start of the first create action
you experience a brief I/O suspension on your source DB instance while the DB snapshot occurs.
Points to consider for creating read replica
you must enable automatic backups on the source DB instance by setting the backup retention period to a value other than 0
Long-running transaction can slow the process of creating the read replica
AWS recommend that you wait for long-running transactions to complete before creating a read replica
When to use Read Replica?
for performance improvement of RDS, (note Multi-AZ is for DR)
for internal systems request data from the RDS DB instance
Scaling beyond the compute or I/O capacity of a single DB instance for read-heavy database workloads
Serving read traffic while the source DB instance is unavailable (data on the read replica may be “stale”)
Business reporting or data warehousing scenarios: You may want business reporting queries to run against a read replica rather than your primary, production DB Instance.
Standby Instance are AZ specific, read replicas can be over multiple regions
Use AWS Secret Manager to protect your RDS database with password and automatic key rotation
ElastiCache for Redis
to improve RDS DB instance speed / performance
Gaming leaderboard, Top 10 players, real-time score update
To create an encrypted RDS from unencrypted RDS
Take a Snapshot of the RDS instance.
Create an encrypted copy of the snapshot.
Restore the RDS instance from the encrypted snapshot
Multi AZ RDS Deployment
RPO less than 1 sec.
Multi AZ RDS deployment is limited to same region, Cross-Region Multi-AZ isn't supported.
The following table showcases the average RPO and RTO metrics you can attain with various HA and DR capabilities of Amazon RDS for SQL Server.
Feature RPO (approx) RTO (approx)
Amazon RDS Multi-AZ 0 1–2 Minutes
Read replica promotion (in-Region) Minutes < 5 Minutes
PITR (in-Region) using automated backups 5 Minutes Minutes–Hours
PITR (cross-Region) using automated backups 6–20 Minutes Minutes–Hours
Snapshot restore Hours Minutes–Hours
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.html
https://aws.amazon.com/rds/faqs/