Domain 3 of 4 · Chapter 4 of 8

Database Services

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Included in this chapter:

  • EC2-hosted vs AWS-managed databases: who owns what
  • The purpose-built database families, and which to pick
  • Migrating databases to AWS: AWS DMS and AWS SCT
  • Exam-pattern recognition: reading CLF-C02 database stems

Which AWS database service fits the workload

Workload needRelational (RDS / Aurora)Key-value NoSQL (DynamoDB)In-memory (ElastiCache)Document / Graph (DocumentDB / Neptune)
Data modelTables, fixed schema, joinsKey-value and document, flexible schemaKey-value held in RAMJSON documents / graph of nodes and edges
Typical use caseTransactional apps, ERP, line-of-businessWeb/mobile at scale, gaming, IoT, serverlessCaching, session store, leaderboardsContent catalogs (DocumentDB); social/fraud/recommendations (Neptune)
Latency profileMillisecondsSingle-digit milliseconds at any scaleMicrosecondsMilliseconds
Scaling styleVertical + read replicasHorizontal, near-unlimited, automaticAdd nodes / scale memoryRead replicas in a cluster
Server managementManaged (engine maintenance by AWS)Serverless (no instances to manage)Managed nodesManaged cluster

Decision tree

Structured tables,joins, transactions?Need Oracle, SQLServer, or Db2?Highly connectedrelationships?JSON documents /MongoDB workload?Just caching hotrepeated reads?Amazon RDSAmazon AuroraAmazonNeptuneAmazonDocumentDBAmazonElastiCacheAmazonDynamoDBYesNoYesNoYesNoYesNoYesNo

Cheat sheet

  • Managed databases remove routine admin
  • Run databases on EC2 only when you must
  • AWS offers purpose-built database families
  • Amazon RDS is managed relational for standard engines
  • Amazon Aurora is AWS's high-performance relational engine
  • Aurora cannot run Oracle, SQL Server, or Db2
  • DynamoDB is serverless single-digit-ms NoSQL
  • DynamoDB is wrong for SQL joins
  • ElastiCache serves microsecond in-memory reads
  • Cache hot repeated reads with ElastiCache
  • DocumentDB is the managed MongoDB-compatible store
  • Neptune is the graph database for connected data
  • AWS DMS moves data with minimal downtime
  • AWS SCT converts the schema for engine changes
  • DMS moves data, SCT converts schema
  • Databases are not for files or warehousing
  • Multi-AZ gives a synchronous standby with automatic failover

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References

  1. https://aws.amazon.com/rds/faqs/
  2. https://aws.amazon.com/rds/aurora/faqs/
  3. https://aws.amazon.com/dynamodb/faqs/
  4. https://aws.amazon.com/elasticache/faqs/
  5. https://aws.amazon.com/documentdb/faqs/
  6. https://aws.amazon.com/neptune/faqs/
  7. https://aws.amazon.com/dms/faqs/