AWS Solutions Architect Patterns: Well-Architected Framework & Designs

Knowing individual AWS services is not the same as knowing how to architect with them. A Solutions Architect combines services into systems that are secure, reliable, cost-efficient, and operationally excellent. AWS has codified the principles behind great cloud architecture in the Well-Architected Framework — and the SAA-C03 exam tests your ability to apply them.

The AWS Well-Architected Framework

The Well-Architected Framework is a set of architectural best practices and design principles organised into six pillars. Use it to evaluate and improve your architectures.

Pillar 1: Operational Excellence

Define everything as code (CloudFormation, CDK, Terraform), make frequent small reversible changes, anticipate failure with game days and runbooks, and learn from all operational events through blameless post-mortems. AWS services: CloudFormation, AWS CDK, Systems Manager, CloudWatch, X-Ray, Config.

Pillar 2: Security

Implement a strong identity foundation with least privilege and MFA, enable traceability (CloudTrail, VPC Flow Logs), apply security at every layer (defence-in-depth), protect data in transit (TLS) and at rest (KMS), and automate security responses with GuardDuty and Security Hub. AWS services: IAM, KMS, CloudTrail, GuardDuty, Security Hub, WAF, Shield, Macie.

Pillar 3: Reliability

Design for automatic failure recovery with health checks and multi-AZ, test recovery procedures by actually restoring backups, scale horizontally, stop guessing capacity with Auto Scaling, and manage change through automation. AWS services: Route 53, ELB, Auto Scaling, RDS Multi-AZ, S3, CloudFormation.

Pillar 4: Performance Efficiency

Use the right tool for the job, go global in minutes with CloudFront and Global Accelerator, use serverless to remove capacity management overhead, and experiment often. AWS services: CloudFront, Lambda, ECS Fargate, DynamoDB, ElastiCache, Global Accelerator.

Pillar 5: Cost Optimisation

Adopt a consumption model (pay only for what you use), measure overall efficiency (cost per transaction), stop spending on undifferentiated heavy lifting by using managed services, and analyse expenditure with tags. AWS services: Cost Explorer, AWS Budgets, Compute Savings Plans, Reserved Instances, Spot Instances, S3 Lifecycle policies, Trusted Advisor.

Pillar 6: Sustainability

Right-size infrastructure, maximise utilisation with Spot and serverless, use lifecycle policies to move data to lower-energy storage classes, and measure with the Customer Carbon Footprint Tool.

Three-Tier Web Architecture

The three-tier architecture is the most commonly tested pattern in the SAA-C03 exam. It separates concerns into three distinct layers, each scalable independently.

┌─────────────────────────────────────────────────────────┐
│                       Internet                          │
└───────────────────────────┬─────────────────────────────┘
                            ↓
┌─────────────────────────────────────────────────────────┐
│              Presentation Tier (Web)                    │
│  CloudFront CDN → ALB → EC2/ECS (public subnets)        │
│  Serves static assets (S3) + dynamic HTML               │
└───────────────────────────┬─────────────────────────────┘
                            ↓
┌─────────────────────────────────────────────────────────┐
│              Application Tier (API)                     │
│  ALB → EC2/ECS/Lambda (private subnets)                 │
│  Business logic, API endpoints                          │
└───────────────────────────┬─────────────────────────────┘
                            ↓
┌─────────────────────────────────────────────────────────┐
│              Data Tier (Database)                       │
│  RDS Multi-AZ (private subnets)                         │
│  ElastiCache Redis (session + query cache)              │
└─────────────────────────────────────────────────────────┘

Security group rules for three-tier: Web tier SG allows 80/443 from internet; App tier SG allows 8080 from Web tier SG only; DB tier SG allows 5432 from App tier SG only. No direct internet access to the application or database tier.

Serverless Architecture Patterns

Serverless means no servers to provision, patch, or scale. You write code; AWS manages the infrastructure.

Core Serverless Services

Serverless REST API Pattern

Client → API Gateway → Lambda → DynamoDB
                     ↓
                 S3 (file storage)
                 SES (email)

Lambda key concepts: maximum execution time is 15 minutes, maximum memory is 10 GB, billed per 1ms of execution, cold starts (~100ms–1s) on first invocation after idle, and concurrency scales to thousands of concurrent executions automatically.

Event-Driven Architecture

In event-driven architecture, components communicate by emitting and consuming events — they are decoupled and do not call each other directly.

Order Service  →  SQS Queue  →  Lambda (process payment)
               →  SNS Topic  →  Lambda (send confirmation email)
                             →  Lambda (update inventory)
                             →  SQS (notify warehouse)

SQS vs SNS vs EventBridge

Disaster Recovery Strategies

AWS defines four DR strategies, ranked from cheapest/slowest to most expensive/fastest:

Choose DR strategy based on your RTO/RPO requirements vs. budget. Most organisations use Warm Standby or Pilot Light for non-critical systems and Multi-Site for mission-critical ones.

Previous: Lesson 8 — High Availability & Auto Scaling | Next: Lesson 10 — SAA-C03 Exam Guide

Part of the AWS Cloud Fundamentals course.

External references:

• AWS Well-Architected Framework whitepaper — all six pillars with detailed guidance