IntermediateDatabases

Database Services: RDS, DynamoDB, Aurora

Choose the right AWS database service by workload pattern, scaling model, and operational responsibility.

What Is It? (ELI5)

RDS is a managed SQL database, DynamoDB is a managed NoSQL key-value/document database, and Aurora is a cloud-optimized relational engine for high performance.

Why Do We Need It?

Apps have different data models and query patterns.
Managed services reduce patching and backup burden.
Correct service choice improves cost and reliability.

How It Works (Technical)

Service	Model	Best For	Azure Equivalent
RDS	Relational (MySQL/PostgreSQL/SQL Server)	Transactional apps with SQL queries	Azure SQL / Azure Database for PostgreSQL/MySQL
DynamoDB	NoSQL key-value/document	High-scale low-latency workloads	Cosmos DB (NoSQL API)
Aurora	Relational, cloud-native	High throughput with managed failover	Azure SQL Hyperscale (approx)

Hands-on

# Create DynamoDB table
aws dynamodb create-table --table-name Orders \
  --attribute-definitions AttributeName=OrderId,AttributeType=S \
  --key-schema AttributeName=OrderId,KeyType=HASH \
  --billing-mode PAY_PER_REQUEST

# List RDS instances
aws rds describe-db-instances --query "DBInstances[].DBInstanceIdentifier" --output table

Debugging Scenario

Problem

Application timeouts after migration to RDS.

Check security group rules between app and DB.
Validate connection pool size and max connections.
Inspect slow query logs and missing indexes.

Interview Questions

Beginner: Difference between RDS and DynamoDB?
RDS is SQL relational; DynamoDB is NoSQL key-value/document.

Intermediate: Why choose Aurora over standard RDS engine?
Better performance/storage architecture with managed HA characteristics.

Scenario: Flash-sale traffic reaches 100k requests/sec. Which DB design fits?
Use DynamoDB for hot key-value access with proper partition design and caching.

Real-world Usage

SaaS platforms commonly use Aurora for core transactions and DynamoDB for session/cart data requiring millisecond reads.

Summary

RDS and Aurora for relational consistency and SQL workloads.
DynamoDB for massive scale and simple access patterns.
Schema and query design drive service choice more than brand preference.