Intermediate14 min read

Database Services

Use AWS managed database services — RDS for relational databases, DynamoDB for NoSQL, ElastiCache for caching, and backup strategies.

Amazon RDS

RDS manages relational databases: PostgreSQL, MySQL, MariaDB, Oracle, and SQL Server. AWS handles provisioning, patching, backups, and failover. Multi-AZ deployments provide automatic failover for high availability.

Read Replicas scale read traffic and serve as failover targets. Automated backups with point-in-time recovery protect against data loss.

Multi-AZ synchronously replicates to standby in another AZ
Read Replicas are asynchronous — eventual consistency
Aurora is AWS cloud-native database with 5x PostgreSQL performance

# Create PostgreSQL RDS instance
aws rds create-db-instance \
  --db-instance-identifier mydb \
  --db-instance-class db.t3.micro \
  --engine postgres \
  --engine-version 16.1 \
  --master-username admin \
  --master-user-password secret \
  --allocated-storage 20 \
  --multi-az \
  --backup-retention-period 7

Amazon DynamoDB

DynamoDB is a fully managed NoSQL key-value and document database. Single-digit millisecond latency at any scale. Pay-per-request or provisioned capacity pricing.

Design around access patterns — define partition key and optional sort key. Use Global Secondary Indexes (GSI) for alternate query patterns. DynamoDB Streams capture changes for event-driven processing.

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

# Query
aws dynamodb get-item \
  --table-name Users \
  --key '{"userId": {"S": "user-123"}}'

ElastiCache

ElastiCache provides managed Redis and Memcached for in-memory caching. Reduce database load and improve response times by caching frequently accessed data.

Redis supports persistence, replication, and complex data structures. Memcached is simpler with multi-threaded performance. Use Redis for session storage, leaderboards, and pub/sub.

# Redis connection from Node.js
import { createClient } from 'redis';

const client = createClient({
  url: 'redis://my-cluster.cache.amazonaws.com:6379',
});
await client.connect();
await client.set('session:abc', JSON.stringify(data), { EX: 3600 });

Backup and Recovery

RDS automated backups capture daily snapshots and transaction logs for point-in-time recovery. Retention period: 1–35 days. Manual snapshots persist until deleted.

DynamoDB Point-in-Time Recovery (PITR) enables restoration to any second within the last 35 days. Enable on-demand backups before major schema changes.

# RDS point-in-time restore
aws rds restore-db-instance-to-point-in-time \
  --source-db-instance-identifier mydb \
  --target-db-instance-identifier mydb-restored \
  --restore-time 2024-01-15T10:00:00Z

Database Selection Guide

RDS/Aurora for relational data with complex queries and transactions. DynamoDB for key-value access patterns at massive scale. ElastiCache for caching layers. DocumentDB for MongoDB-compatible workloads. Redshift for data warehousing.

Prefer managed services over self-managed databases on EC2. Managed services handle patching, backups, and failover automatically.