Skip to main content

Relational Databases (RDS/Aurora)

Relational Database Service (RDS)​

  • Managed DB service for DB use SQL as a query language
  • It allows you to create databases in the cloud that are managed by AWS
    • Postgres
    • MySQL
    • MariaDB
    • Oracle
    • Microsoft SQL Server
    • IBM DB2
    • Aurora (AWS Proprietary database)

Using RDS versus deploying DB on EC2​

  • RDS is a managed service:
    • Automated provisioning, OS patching
    • Continuous backups and restore to specific timestamp (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)
    • Storage backed by EBS
  • BUT you can’t SSH into your instances

Storage Auto Scaling​

  • Helps you increase storage on your RDS DB instance dynamically
  • When RDS detects you are running out of free database storage, it scales automatically
    • Avoid manually scaling your database storage
    • You have to set Maximum Storage Threshold (maximum limit for DB storage)
  • Automatically modify storage if:
    • Free storage is less than 10% of allocated storage
    • Low-storage lasts at least 5 minutes
    • 6 hours have passed since last modification
  • Useful for applications with unpredictable workloads
  • Supports all RDS database engines

Read Replicas for read scalability​

  • 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 own DB
  • Applications must update the connection string to leverage read replicas

rds-read-replicas

Example Use Case​

  • 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 only used for SELECT statements (not INSERT, UPDATE, DELETE)

read-replica-use-case

Read Replicas – Network Cost​

  • In AWS there’s a network cost when data goes from one AZ to another
  • For RDS Read Replicas within the same region, you don’t pay that fee

rds-network-cost

Multi AZ (Disaster Recovery)​

  • SYNC replication
  • One DNS name – automatic app failover to standby
    • Increases availability
  • Failover in case of loss of AZ, loss of network, instance or storage failure
  • No manual intervention in apps
  • Not used for scaling

Note: The Read Replicas are setup as Multi AZ for Disaster Recovery (DR)

rds-disaster-recovery

From Single-AZ to Multi-AZ​

  • Zero downtime operation (no need to stop the DB)
  • Just click on “modify” for the database
  • The following happens internally:
    • A snapshot is taken
    • A new DB is restored from the snapshot in a new AZ
    • Synchronization is established between the two databases

multi-az-rds

RDS Proxy​

  • Fully managed database proxy for RDS
  • Allows apps to pool and share DB connections established with the database
  • Improving database efficiency by reducing the stress on database resources (e.g., CPU, RAM) and minimize open connections (and timeouts)
  • Serverless, autoscaling, highly available (multi-AZ)
  • Reduced RDS & Aurora failover time by up 66%
  • Supports RDS (MySQL, PostgreSQL, MariaDB, MS SQL Server) and Aurora (MySQL, PostgreSQL)
  • No code changes required for most apps
  • Enforce IAM Authentication for DB, and securely store credentials in AWS Secrets Manager
  • RDS Proxy is never publicly accessible (must be accessed from VPC)

rds-proxy

Amazon 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 improvement over MySQL on RDS, over 3x the performance of Postgres on RDS
  • Aurora storage automatically grows in increments of 10GB, up to 128 TB
  • Aurora can have up to 15 replicas and the replication process is faster than MySQL (sub 10 ms replica lag)
  • Failover in Aurora is instantaneous. It’s HA (High Availability) native
  • Aurora costs more than RDS (20% more) – but is more efficient

High Availability and Read Scaling​

  • 6 copies of your data across 3 AZ:
    • 4 copies out of 6 needed for writes
    • 3 copies out of 6 need for reads
    • Self healing with peer-to-peer replication
    • Storage is striped across 100s of volumes
  • One Aurora Instance takes writes (master)
  • Automated failover for master in less than 30 seconds
  • Master + up to 15 Aurora Read Replicas serve reads
  • Support for Cross Region Replication

aurora

DB Cluster​

aurora-cluster

Features​

  • Automatic fail-over
  • Backup and Recovery
  • Isolation and security
  • Industry compliance
  • Push-button scaling
  • Automated Patching with Zero Downtime
  • Advanced Monitoring
  • Routine Maintenance
  • Backtrack: restore data at any point of time without using backups

RDS & Aurora Security​

  • At-rest encryption:
    • Database master & replicas encryption using AWS KMS – must be defined as launch time
    • If the master is not encrypted, the read replicas cannot be encrypted
    • To encrypt an un-encrypted database, go through a DB snapshot & restore as encrypted
  • In-flight encryption: TLS-ready by default, use the AWS TLS root certificates client-side
  • IAM Authentication: IAM roles to connect to your database (instead of username/pw)
  • Security Groups: Control Network access to your RDS / Aurora DB
  • No SSH available except on RDS Custom
  • Audit Logs can be enabled and sent to CloudWatch Logs for longer retention