AWS Managed Services

Managed Services Ecosystem

RDS — Relational Database Service

RDS manages relational databases so you don't have to handle installation, patching, backups, or replication. It supports PostgreSQL, MySQL, MariaDB, Oracle, SQL Server, and Amazon Aurora.

RDS vs. Self-Managed on EC2

# Create a PostgreSQL RDS instance
aws rds create-db-instance \
  --db-instance-identifier my-postgres \
  --db-instance-class db.t3.micro \
  --engine postgres \
  --engine-version 16.1 \
  --master-username admin \
  --master-user-password MySecurePass123! \
  --allocated-storage 20 \
  --multi-az \
  --backup-retention-period 7

# Create a read replica for scaling reads
aws rds create-db-instance-read-replica \
  --db-instance-identifier my-postgres-replica \
  --source-db-instance-identifier my-postgres

DynamoDB — Serverless NoSQL

DynamoDB is a fully managed NoSQL database with single-digit millisecond latency at any scale. No servers to manage, no capacity planning — it scales automatically.

Key Concepts

• Table — Collection of items (like a SQL table)
• Partition Key — Primary key used for data distribution (must be unique or combined with sort key)
• Sort Key — Optional secondary key for range queries within a partition
• GSI (Global Secondary Index) — Query by different attributes

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

# Put an item
aws dynamodb put-item --table-name Orders \
  --item '{
    "customerId": {"S": "CUST-001"},
    "orderId": {"S": "ORD-2026-0001"},
    "total": {"N": "59.99"},
    "status": {"S": "shipped"}
  }'

# Query all orders for a customer
aws dynamodb query --table-name Orders \
  --key-condition-expression "customerId = :cid" \
  --expression-attribute-values '{":cid": {"S": "CUST-001"}}'

SQS & SNS — Messaging

These two services decouple your components so they don't need to communicate directly.

SQS vs. SNS

# Create an SQS queue
QUEUE_URL=$(aws sqs create-queue --queue-name order-processing \
  --query 'QueueUrl' --output text)

# Send a message
aws sqs send-message --queue-url $QUEUE_URL \
  --message-body '{"orderId": "ORD-001", "action": "process"}'

# Receive and delete a message
MSG=$(aws sqs receive-message --queue-url $QUEUE_URL \
  --query 'Messages[0]' --output json)
# ... process the message ...
aws sqs delete-message --queue-url $QUEUE_URL \
  --receipt-handle $(echo $MSG | jq -r '.ReceiptHandle')

# Create an SNS topic and subscribe email
TOPIC_ARN=$(aws sns create-topic --name alerts \
  --query 'TopicArn' --output text)
aws sns subscribe --topic-arn $TOPIC_ARN \
  --protocol email --notification-endpoint [email protected]

CloudWatch — Monitoring & Observability

CloudWatch collects metrics, logs, and events from all AWS services. It's your single pane of glass for monitoring.

• Metrics — CPU, memory, request count, error rate (auto-collected for most services)
• Alarms — Trigger actions when metrics cross thresholds (e.g., auto-scale, send SNS alert)
• Logs — Centralized log storage from EC2, Lambda, containers, etc.
• Dashboards — Custom visualizations of your metrics

# Create an alarm: alert if CPU > 80% for 5 minutes
aws cloudwatch put-metric-alarm \
  --alarm-name high-cpu-alarm \
  --metric-name CPUUtilization \
  --namespace AWS/EC2 \
  --statistic Average \
  --period 300 \
  --threshold 80 \
  --comparison-operator GreaterThanThreshold \
  --evaluation-periods 1 \
  --dimensions Name=InstanceId,Value=i-0abc123def456 \
  --alarm-actions arn:aws:sns:us-east-1:123456789012:alerts

# Query logs
aws logs filter-log-events \
  --log-group-name /aws/lambda/processUpload \
  --filter-pattern "ERROR"

CloudFormation — Infrastructure as Code

CloudFormation lets you define your entire AWS infrastructure in YAML or JSON templates. Instead of clicking through the console, you version-control your infrastructure like application code.

# template.yaml — Create a VPC + EC2 instance
AWSTemplateFormatVersion: '2010-09-09'
Description: Simple web server stack

Resources:
  WebServerInstance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t3.micro
      ImageId: ami-0c02fb55956c7d316
      SecurityGroupIds:
        - !Ref WebServerSG
      Tags:
        - Key: Name
          Value: my-web-server

  WebServerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow HTTP
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0

Outputs:
  InstanceId:
    Value: !Ref WebServerInstance
  PublicIP:
    Value: !GetAtt WebServerInstance.PublicIp

# Deploy the stack
aws cloudformation create-stack \
  --stack-name my-web-stack \
  --template-body file://template.yaml

# Update an existing stack
aws cloudformation update-stack \
  --stack-name my-web-stack \
  --template-body file://template.yaml

# Delete everything created by the stack
aws cloudformation delete-stack --stack-name my-web-stack

Interview Questions