Task Statement 2.1: Design scalable and loosely coupled architectures.

📘AWS Certified Solutions Architect – (SAA-C03)

1. Understanding Requirements (VERY IMPORTANT)

Before choosing any service, always identify:

1. Workload Type

Web application
Batch processing
Real-time processing
Analytics workload

2. Key Factors

You must evaluate:

Scalability → Does traffic change frequently?
Availability → Must it always be online?
Performance → Fast response required?
Cost → Minimize cost?
Management → Fully managed or self-managed?
Durability → How important is data safety?

👉 In the exam, questions often hide the answer inside these requirements.

2. Compute Services (Processing Power)

Compute services run your application code.

Main AWS Compute Options

1. Amazon EC2 (Virtual Servers)

Use when:

Full control over OS is required
Custom software installation is needed
Long-running applications

Key features:

Flexible instance types
Auto Scaling support
Works with load balancers

Best for:

Traditional applications
Lift-and-shift migrations

2. AWS Lambda (Serverless Compute)

Use when:

Event-driven workloads
No server management required
Automatic scaling needed

Key features:

Runs code without servers
Pay per execution
Scales instantly

Best for:

API backends
Event processing (e.g., file uploads)

3. Amazon ECS / EKS (Containers)

Use when:

Applications are containerized
Need microservices architecture

Difference:

ECS → Easier, AWS-managed
EKS → Kubernetes-based, more control

Best for:

Scalable microservices
DevOps-heavy environments

4. AWS Fargate

Use when:

Running containers without managing servers

Best for:

Serverless containers

5. AWS Elastic Beanstalk

Use when:

Want easy deployment without managing infrastructure

Best for:

Beginners
Web apps

Compute Decision Tips (Exam)

Requirement	Best Choice
Full control	EC2
No server management	Lambda
Containers	ECS / EKS
Serverless containers	Fargate
Quick deployment	Elastic Beanstalk

3. Storage Services (Data Storage)

Storage depends on how data is accessed and used.

Main Storage Types

1. Amazon S3 (Object Storage)

Use when:

Storing files, images, backups
Static website hosting

Key features:

Highly durable (11 9’s durability)
Scalable
Multiple storage classes

Storage classes:

Standard → frequent access
IA → infrequent access
Glacier → archival

2. Amazon EBS (Block Storage)

Use when:

Attached to EC2
Needs low-latency access

Best for:

Databases
OS disks

3. Amazon EFS (File Storage)

Use when:

Multiple EC2 instances need shared access

Best for:

Shared file systems
Linux workloads

4. Instance Store

Use when:

Temporary storage
Data loss acceptable

5. AWS Backup / Glacier

Use when:

Long-term backup and archive

Storage Decision Tips (Exam)

Requirement	Best Choice
File storage (shared)	EFS
Block storage	EBS
Object storage	S3
Temporary storage	Instance Store
Archive	Glacier

4. Database Services

Choosing the correct database is very important in the exam.

1. Relational Databases (SQL)

Amazon RDS

Use when:

Structured data
ACID compliance needed

Supported engines:

MySQL, PostgreSQL, MariaDB, Oracle, SQL Server

Features:

Automated backups
Multi-AZ for high availability
Read replicas for scaling

Amazon Aurora

Use when:

Need high performance
Cloud-optimized database

Benefits:

Faster than standard RDS
Auto scaling storage

2. NoSQL Database

Amazon DynamoDB

Use when:

Massive scale
Low latency (milliseconds)
Key-value or document data

Features:

Fully managed
Auto scaling
Serverless

3. In-Memory Database

Amazon ElastiCache

Use when:

Need fast caching
Reduce database load

Engines:

Redis
Memcached

4. Data Warehouse

Amazon Redshift

Use when:

Analytics
Large-scale reporting

5. Specialized Databases

Service	Use Case
Neptune	Graph data
DocumentDB	JSON/document data
Timestream	Time-series data

Database Decision Tips (Exam)

Requirement	Best Choice
Structured data	RDS
High performance relational	Aurora
NoSQL, scalable	DynamoDB
Caching	ElastiCache
Analytics	Redshift

5. Networking Services

Networking controls how systems communicate securely and efficiently.

Core Networking Services

1. Amazon VPC

Isolated network environment
Define IP ranges, subnets

2. Subnets

Public subnet → internet access
Private subnet → internal systems

3. Internet Gateway

Allows internet access

4. NAT Gateway

Allows private resources to access internet

5. Elastic Load Balancer (ELB)

Distributes traffic:

Types:

ALB → HTTP/HTTPS
NLB → TCP/UDP (high performance)
GWLB → security appliances

6. Route 53

DNS service
Routing policies (latency, failover, etc.)

7. CloudFront

Content Delivery Network (CDN)
Reduces latency

8. Security Groups & NACLs

Security Groups → instance-level firewall
NACL → subnet-level firewall

Networking Decision Tips (Exam)

Requirement	Best Choice
Global DNS	Route 53
Load balancing	ELB
Private networking	VPC
Faster content delivery	CloudFront
Secure access	Security Groups

6. Putting It All Together (Architecture Thinking)

In the exam, you will often combine services:

Example Pattern (Typical Exam Scenario)

Frontend → CloudFront + S3
Backend → Lambda or EC2
Database → DynamoDB or RDS
Load Balancer → ALB
Networking → VPC with public/private subnets

7. Key Exam Tips

1. Always Match Requirements

Don’t choose services randomly
Match keywords in the question

2. Look for Keywords

Keyword	Meaning
“Fully managed”	Avoid EC2
“Serverless”	Use Lambda/DynamoDB
“Low latency”	DynamoDB / ElastiCache
“Shared storage”	EFS
“High throughput”	S3 or EBS

3. High Availability

Use Multi-AZ
Use Load Balancers
Use Auto Scaling

4. Cost Optimization

Use serverless when possible
Use correct storage class

5. Scalability

Use Auto Scaling
Use managed services

8. Quick Summary (Memory Section)

Compute → EC2, Lambda, ECS
Storage → S3, EBS, EFS
Database → RDS, DynamoDB, Aurora
Networking → VPC, ELB, Route 53

Final Advice for Exam

Read the question carefully
Identify requirements first
Eliminate wrong options
Choose the simplest and most scalable solution