AWS Case Studies: Failures, Migrations, and Lessons Learned

1. Failure: The Startup That Overprovisioned (Exploding Costs)

Background

A SaaS startup with:

• 50 customers
• 200 active users
• Oversized architecture
• AWS costs: $2,500/month

Issues Identified

• EC2 overuse: 10 t3.large instances (~$800/month)
• Database: 2 RDS db.r5.xlarge instances (~$1,000/month)
• ElastiCache: 2 Redis clusters (~$400/month)
• CloudFront: Excessive configuration (~$300/month)

Solution Adopted

• Migration to ECS Fargate: 2 services, 2 vCPU (~$150/month)
• RDS downsizing: 1 db.t3.small instance (~$50/month)
• ElastiCache removal: Not needed at this scale
• CloudFront optimization: Minimal configuration (~$10/month)

Result

• Reduced cost: From $2,500/month to ~$210/month
• Performance: Similar for the current load
• Savings: 91% cost reduction

Lessons Learned

• Start small and scale as needed
• Avoid premature overprovisioning
• Monitor costs regularly
• Use serverless services whenever possible

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2. Failure: E-commerce with a Monolithic Architecture (Scaling Problems)

Background

An online store with:

• 5,000 orders/month
• 20,000 products
• Monolithic architecture on EC2
• Problems during traffic spikes

Issues Identified

• EC2 bottleneck: 4 t3.large instances (~$320/month)
• Database: 1 RDS db.r5.large instance (~$300/month)
• Scaling problems: Slowness during spikes
• High costs: ~$700/month for average performance

Solution Adopted

• Migration to a serverless architecture:
  • Frontend: S3 + CloudFront (~$50/month)
  • Backend: Lambda + API Gateway (~$20/month)
  • Database: DynamoDB (~$50/month)
  • Payments: Stripe via Lambda (~$30/month)

Result

• Reduced cost: From $700/month to ~$150/month
• Performance: Automatic scaling during spikes
• Availability: Significant improvement
• Maintenance: Drastic reduction

Lessons Learned

• Avoid monolithic architectures for e-commerce
• Use serverless services for automatic scaling
• Separate components for better resilience
• Optimize costs per transaction

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3. Migration: From Heroku to AWS (Control and Costs)

Background

A web application with:

• 200 customers
• 1,000 active users
• Deployed on Heroku
• Heroku costs: $500/month

Issues Identified

• Heroku costs: $500/month for limited performance
• Lack of control: Limited configuration
• Limited scaling: Restricted options
• Vendor lock-in: Dependence on Heroku

Solution Adopted

• Migration to AWS:
  • Application: ECS Fargate (~$150/month)
  • Database: RDS PostgreSQL (~$100/month)
  • Storage: S3 (~$5/month)
  • CDN: CloudFront (~$5/month)

Result

• Reduced cost: From $500/month to ~$260/month
• Control: Full access to the infrastructure
• Performance: Significant improvement
• Flexibility: Multiple scaling options

Lessons Learned

• Evaluate the long-term costs of PaaS platforms
• Weigh control against simplicity
• Plan the migration in detail
• Train the team on the new technologies

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4. Migration: From On-Premises to AWS (Modernization)

Background

A traditional company with:

• 500 employees
• Legacy on-premises applications
• Infrastructure costs: $10,000/month
• Need for modernization

Issues Identified

• High costs: Server maintenance, electricity, cooling
• Limited availability: No geographic redundancy
• Difficult scaling: Manual and slow process
• Security: Outdated configuration

Solution Adopted

• Migration to AWS:
  • Applications: EC2 Auto Scaling (~$2,000/month)
  • Database: RDS Multi-AZ (~$3,000/month)
  • Storage: S3 + EFS (~$500/month)
  • Security: WAF + Shield (~$1,000/month)

Result

• Reduced cost: From $10,000/month to ~$6,500/month
• Availability: Significant improvement
• Security: Automatic updates
• Flexibility: Automatic scaling

Lessons Learned

• Plan the migration in phases
• Train the team beforehand
• Use AWS migration tools
• Consider long-term costs

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5. Failure: The Startup That Underprovisioned (Outages)

Background

A growing startup with:

• 1,000 customers
• 5,000 active users
• Undersized architecture
• Frequent outages

Issues Identified

• Elastic Beanstalk: 1 t3.micro instance (~$8/month)
• RDS: 1 db.t3.micro instance (~$12/month)
• Outages: Frequent downtime
• Performance: Chronic slowness

Solution Adopted

• Migration to a robust architecture:
  • Application: ECS Fargate (~$150/month)
  • Database: RDS db.t3.small Multi-AZ (~$100/month)
  • Cache: ElastiCache (~$50/month)
  • Monitoring: CloudWatch (~$20/month)

Result

• Increased cost: From $20/month to ~$320/month
• Availability: 99.9% vs. 95% previously
• Performance: Significant improvement
• Customer satisfaction: Notable increase

Lessons Learned

• Don’t sacrifice quality for cost
• Monitor performance metrics
• Plan for growth in advance
• Invest in robustness

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Comparison Table of Failures and Migrations

Scenario	Main Problem	Solution	Savings/Cost
Overprovisioning	Excessive costs	Downsizing	-91% ($2,500 → $210)
Monolithic architecture	Limited scaling	Serverless	-79% ($700 → $150)
Heroku migration	Limited costs and control	Native AWS	-48% ($500 → $260)
On-premises	High costs and maintenance	AWS cloud	-35% ($10,000 → $6,500)
Underprovisioning	Frequent outages	Robust architecture	+1,500% ($20 → $320)

Tips to Avoid Failures:

1. For Overprovisioning:

   • Start small
   • Use auto scaling
   • Monitor utilization metrics
   • Optimize regularly

2. For Monolithic Architectures:

   • Design for scale from the start
   • Use microservices or serverless
   • Test load spikes
   • Plan for growth

3. For Migrations:

   • Plan in detail
   • Test in a staging environment
   • Train the team beforehand
   • Plan for a rollback

4. For Underprovisioning:

   • Monitor performance metrics
   • Plan for growth
   • Invest in robustness
   • Don’t sacrifice quality for cost

Key Takeaways:

Failures are learning opportunities:

• Monitor costs and performance regularly
• Adapt the architecture to the growth stage
• Invest in team training
• Plan for the long term while staying agile