AWS Databases Notes

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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.

Database Notes


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)

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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 ...

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