AWS RDS - Relational Database Service

• It is a managed database service for relational databases
• It allows us to create databases in the cloud that are managed by AWS
• RDS offerings provided by AWS:
  • PostreSQL
  • MySQL
  • MariaDB
  • Oracle
  • Microsoft SQL Server
  • Aurora
• Advantages of AWS RDS over deploying an relational database on EC2:
  • RDS is a managed service, meaning:
    • Automated provisioning, OS patching
    • Continuous backups and restore to specific timestamp (Point in Time Restore)
    • Monitoring dashboards
    • Read replicas
    • Multi AZ setup
    • Maintenance windows for upgrades
    • Scaling capability (vertical and horizontal)
    • Storage backed by EBS (GP2 or IO)
• Disadvantages:
  • No SSH into the instance which hosts the database

RDS Backups

• Backups are automatically enabled in RDS
• AWS RDS provides automated backups:
  • Daily fill backup of the database (during the maintenance window)
  • Transaction logs are backed-up by RDS every 5 minutes which provides the ability to do point in time restores
  • There is a 7 day retention for the backups which can be increased to 35 days
• DB Snapshots:
  • There are manually triggered backups by the users
  • Retention can be as long as the user wants
  • Helpful for retaining the state of the database for longer period of time

RDS Read Replicas

• Read replicas helps to scale the read operations
• We can create up to 5 read replicas
• These replicas can be within AZ, cross AZ or in different regions
• The data between the main database and the read replicas is replicated asynchronously => reads are eventually consistent
• Read replicas can be promoted into their own database
• Use case for read replicas:
  • Production database is up and running taking on normal load
  • There is a new feature for running some reporting for analytics which may cause slow downs and may overload the database
  • To fix this we can create read replicas for reporting
• Read replicas are used for SELECT operations (not INSERT, UPDATE, DELETE)
• Network cost for read replicas:
  • In AWS there is network cost if data goes from one AZ to another
  • In case of cross AZ replication, additional costs may incur because of network traffic
  • To reduce costs, we could have the read replicas in the same AZ

RDS Multi AZ (Disaster Recovery)

• RDS Multi AZ replication is done using synchronous replication
• In case of multi AZ configuration we get one DNS name
• In case of the main database goes down, the traffic is automatically re-routed to the failover database
• Multi AZ is not used for scaling
• The read replicas can be set up as Multi AZ for Disaster Recovery

RDS Security

Encryption

• AWS RDS provides rest encryption: possibility to encrypt the master and read replicas with AWS KMS - AES-256 encryption
  • Encryption has to be defined at the launch time
  • If the master is not encrypted, the read replicas cannot be encrypted
  • Transparent Data Encryption (TDE) is available for Oracle and SQL Server
• In-flight encryption: uses SSL certificates to encrypt data from client to RDS in flight
  • It is required SSL a trust certificate when connecting to database
  • To enforce SSL:
    • PostgeSQL: rds.force_ssl=1 in the AWS RDS Console (Parameter Groups)
    • MySQL: GRANT USAGE ON *.* To 'user'@'%' REQUIRE SSL;
• Encrypting RDS backups:
  • Snapshots of un-encrypted RDS databases are un-encrypted
  • Snapshots of encrypted RDS databases are encrypted
  • We can copy an un-encrypted snapshot into an encrypted one
• Encrypt an un-encrypted RDS database:
  • Create a snapshot
  • Copy the snapshot and enable encryption for the snapshot
  • Restore the database from the encrypted snapshot
  • Migrate application from the old database to the new one and delete the old database

Network Security and IAM

• Network security:
  • RDS databases are usually deployed within a private subnet
  • RDS security works by leveraging security groups (similar to EC2), they control who can communicate with the database instance
• Access management:
  • There are IAM policies which help control who can manage an AWS RDS database (through the RDS API)
  • Traditional username/password can be used to login into the database
  • IAM-based authentication can be used to login into MySQL and PostgreSQL
• IAM authentication:
  • IAM database authentication works with MySQL and PostgreSQL
  • We don't need a password to authenticate, just an authentication token obtained through IAM and RDS API calls
  • The token has a lifetime of 15 minutes
  • Benefits:
    • Network in/out must be encrypted using SSL
    • IAM is used to centrally manage users instead of DB credentials
    • We can manage IAM roles and EC2 instance profiles for easy integration

Security Summary

• Encryption at rest:
  • It is done only when the database is created
  • To encrypt an existing database, we have create a snapshot, copy it as encrypted, and create an encrypted database from the snapshot
• Our responsibility:
  • Check the ports/IP/security groups inbound rules
  • Take care of database user creation and permissions or manage them through IAM
  • Create a database with or without public access
  • Ensure parameter groups or DB is configured to only allow SSL connections
• AWS responsibility:
  • DB patching
  • Underlying OS patching and updates