Hello Readers,

This is part 3 of the 5-part Series on cracking the AWS Solutions Architect - Associate Exam. Click here for part 2 - AWS EC2.

I've divided the notes into a 5 part series.

• Part 1: Introduction and AWS S3
• Part 2: AWS EC2
• Part 3: Databases
• Part 4: DNS, VPC, and HA(High-Availability)
• Part 5: Application Services and Serverless + Bonus

Database Notes

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Database in AWS:

1. RDS (OLTP-Online transaction processing) - Ex: give order ID, returns all data
   • SQL Server
   • Oracle
   • MySQL Server
   • PostgreSQL
   • Aurora
   • MariaDB
2. NoSQL
   • DynamoDB
3. Data Warehouse (OLAP-Online analytical processing) - For complex analytics & BI.
   • Redshift

4. Elasticache - improves the performance of DB by caching frequent queries.

   • Two types
     • Memcache
     • Redis
   • You can set up an Autoscaling group that can auto-scale Cache nodes based on CPU usage.

Key Features of RDS

• Multi-AZ - For disaster recovery
• Read Replicas - For Performance ( Max 5 copies for a DB )

Types of RDS backups

• Automated Backups
  • point-in-time recovery;
  • Retention period - 1 to 35 days;
  • Backups stored in S3 (for free)
  • Takes 1 daily snapshot and transactional logs.
  • These are deleted when RDS is deleted
• Database Snapshots
  • Manual snapshots
  • These are NOT deleted when RDS is deleted

General RDS Notes

• [NEW] You can autoscale using RDS Auto Scaling groups
• Two ways to cope with heavy DB load - Elasticache & Read replica
• Read replica is mainly for Performance
• Multi-AZ is mainly for Disaster Recovery
• Cross-region Read replica can be created for Disaster Recovery

DynamoDB

• Stored on SSD - Hence fast
• Spread across 3 AZ
• DynamoDB allows for the storage of large text and binary objects, but there is a limit of 400 KB.
• Has DAX(DynamoDb Accelerator) - in-memory cache(for performance) - It is similar to Elasticache for RDS.
• Two types:
  • Eventual consistency Read (default) - takes around 1 second to update
  • Strong consistency Read - updates Within 1 second and can be read

RedShift

• Single Node ( 160Gb )
• Multi-Node
  • Leader Node (manages client connection and received requests)
  • Compute Node (Stores data and performs computations). Up to 128 nodes.
• Has Advanced Compression -Columnar compression(data in the column is of the same type)
• Massively Parallel Processing (MPP)
• Backups are taken by default with 1-day retention. & Max = 35 days (similar to RDS)
• It maintains 3 copies of data - Original & Replica on the compute node. Backup in S3.
• Charged only for compute node - Not for Leader node
• No multi-AZ support. It can only be in 1 AZ.

Aurora

• Start with 10GB. Scales in 10Gb Increments. Up to 64TB
• Compute resource up to 32vCPUs and 244Gb of memory
• 2 copies in each AZ. Minimum of 3 AZ. So 6 copies of your data.
• Types of Aurora replicas:
  • Aurora Replicas (max 15)
  • MySQL Read Replicas (max 5)
  • PostgreSQL (max 1)

Aurora Serverless

• Simple Cost-effective option for infrequent, intermittent, or unpredictable workloads
• Automatically start-up shut down, and scale capacity up or down based on your application's needs

Continue reading Part 4 - AWS Route53, VPC, and HA ...