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RDS: Relational Database Service

A managed DB service for DB use SQL a query

It allows you to create databases in the cloud that are

  • Postgres
  • Oracle
  • MySQL
  • MariaDB
  • Microsoft SQL Server
  • Aurora (AWS proprietary database)

Advantages of RDS over deploying a database in EC2

  • Managed service
  • OS patching level
  • Continuous backups and restore to specific timestamps (Point in Time Restore)
  • Monitoring dashboards
  • Read replicas for improved read performance
  • Multi AZ setup for DR (Disaster Recovery)
  • Maintenance windows for upgrades
  • Scaling capability (vertical and horizontal)
  • But you can’t SSH into your instances (amazon manages them for you)

RDS Read replicas for read scalability

  • Up to 15 read replicas(MySQL, MariaDB and PostgreSQL) and 5 read replicas(Oracle and SQL Server)
  • Within AZ, Cross AZ or Cross region
  • Replication is Async, so reads are eventually consistent
  • Replicas can be promoted to their own DB
  • Applications must update the connection string to leverage read replicas
  • To enable read replicas, you need to enable backups

RDS Read Replicas – Use Cases

  • You have a production database that is taking on normal load
  • You want to run a reporting application to run some analytics
  • You create a Read Replica to run the new workload there
  • The production application is unaffected
  • Read replicas are used for SELECT (=read) only kind of statements (not INSERT, UPDATE, DELETE)

RDS Read Replicas – Network Cost

  • In AWS there’s a network cost when data goes from one AZ to another
  • To reduce the cost, you can have your Read Replicas in the same AZ

RDS Multi AZ (Disaster Recovery)

  • SYNC replication
  • One DNS name - automatic app failover to standby
  • Increase availability
  • Failover in case of loss of AZ, loss of network, instance or storage failure
  • No manual intervention in apps
  • Not used for scaling (only disaster recovery)

RDS Backups

  • Backups are automatically enabled in RDS
  • Automated backups:
    • Daily full snapshot of the database
    • Capture transaction logs in real time
    • Ability to restore to any point in time
    • 7 days retention (can be increased to 35 days)
  • DB Snapshots:
    • Manually triggered by the user
    • Retention of backup for as long as you want

RDS Encryption

  • Encryption at rest capability with AWS KMS - AES-256 encryption
  • SSL certificates to encrypt data to RDS in flight
  • To enforce SSL:
    • PostgreSQL: rds.force_ssl=1 in the AWS RDS Console (parameter groups)
  • TO connect using SSL:
    • Provide the SSL Trust certificate (can be downloaded from AWS)
    • Provide SSL options when connection to the database

RDS Encryption Operations

  • Encrypting RDS backups
    • Snapshots of un-encrypted RDS databases are un-encrypted
    • Snapshots of encrypted RDS databases are encrypted
    • Can copy a snapshot into an encrypted one
  • To encrypt an un-encrypted RDS database:
    • Create a snapshot of the un-encrypted database
    • Copy the snapshot and enable encryption for the snapshot
    • Restore the database from the encrypted snapshot
    • Migrate applications to the new database, and delete the old database

RDS Security

  • RDS databases are usually deployed within a private subnet, not in a public one
  • RDS Security works by leveraging security groups (the same concept as for EC2 instances) - it controls who can communicate with RDS
  • IAM policies help control who can manage RDS
  • Traditional username and password can be used to login to the database
  • IAM users can now be used too (for MySQL / Aurora - New)

RDS vs. Aurora

  • Aurora is a proprietary technology from AWS (not open sourced)
  • Postgres and MySQL are both supported as Aurora DB (that means your drivers will work as if Aurora was a Postgres or MySQL database)
  • Aurora is “AWS cloud optimized” and claims 5x performance improvements over MySQL on RDS, over 3x the performance of Postgres on RDS
  • Aurora storage automatically grows in increments of 10GB, up to 64 TB
  • Aurora can have 15 replicas while MySQL has 5, and the replication process is faster (sub 10 ms replica lag)
  • Failover in Aurora is instantaneous. It’s HA native.
  • Aurora costs more than RDS (20% more) - but is more efficient
  • Aurora supports for cross region replication

Aurora DB Cluster

  • writer endpoint : pointing to the master
  • reader endpoint: connection load balancing

Aurora Security

  • Similar to RDS because uses the same engines
  • Encryption at rest using KMS
  • Automated backups, snapshots and replicas are also encrypted
  • Encryption in flight using SSL (same process as MySQL or Postgres)
  • Possibility to authenticate using IAM token (same method as RDS)
  • You are responsible for protecting the instance with security groups
  • You can’t SSH

Aurora Serverless

  • Automated database instantiation and auto-scaling based on actual usage
  • Good for infrequent, intermittent or unpredictable workloads
  • No capacity planning needed
  • Pay per second, can be more cost-effective

Global Aurora

  • Aurora Cross Region Read Replicas:
    • Useful for disaster recovery
    • Simple to put in place
  • Aurora Global Database (recommended):
    • 1 Primary Region (read / write)
    • Up to 5 secondary (read-only) regions, replication lag is less than 1 second
    • Up to 16 Read Replicas per secondary region
    • Helps for decreasing latency • Promoting another region (for disaster recovery) has an RTO of < 1 minute