Common AWS Mistakes to Avoid

From Security Missteps to Budget Blowouts – A Guide to Avoiding the Most Costly Errors in AWS

Whether you’re a beginner or an experienced cloud engineer, AWS mistakes can lead to serious problems—security breaches, outages, or surprise bills.

In this chapter, we’ll cover:

• The most frequent mistakes users make
• Real-world consequences
• How to prevent them with best practices

1. Making S3 Buckets Public by Mistake

Problem:
Users often leave S3 buckets open to the public, exposing sensitive files, logs, or backups.

Risks:

• Data breaches
• Compliance violations
• Public shaming via “leaky buckets”

Prevention:

• Block Public Access (BPA) globally or per bucket
• Enable bucket policies for specific access
• Use AWS Config to audit bucket settings

2. Using Root Account for Daily Tasks

Problem:
The AWS root user has full power. Using it regularly is dangerous.

Risks:

• Accidental deletion
• Credential theft
• Untraceable access (no IAM policies)

Prevention:

• Create IAM users/roles
• Enable MFA for root
• Store root credentials securely (and rarely use them)

3. Forgetting to Stop Idle EC2/RDS Instances

Problem:
Leaving dev/test servers running over weekends or holidays.

Result:
You’re billed per second/hour—even if no one is using the instance.

Prevention:

• Schedule auto-stop/start (Lambda + EventBridge)
• Use CloudWatch to track idle CPU
• Tag and group non-production resources

4. Wrong EC2 Instance Types or Sizes

Problem:
Using too-large or underpowered instances

Result:

• Wasted cost
• Poor app performance

Prevention:

• Use Compute Optimizer for right-sizing
• Monitor performance via CloudWatch
• Test performance under load

5. Ignoring Security Groups and NACLs

Problem:
Allowing 0.0.0.0/0 access on ports like SSH (22), RDP (3389), or databases

Risks:

• Easy target for brute-force or port scans
• Unauthorized access

Prevention:

• Use strict IP whitelisting
• Block unused ports
• Use Bastion Hosts or Session Manager for SSH

6. Over-Permissioned IAM Policies

Problem:
Giving AdministratorAccess or *:* permissions to users/roles

Risks:

• Misuse or privilege escalation
• Security audits may fail

Prevention:

• Apply Least Privilege principle
• Use IAM Access Analyzer
• Rotate credentials regularly

7. No Cost Visibility or Budgeting

Problem:
No alerting when spend crosses a threshold

Consequence:
Shocking bills at month’s end

Prevention:

• Set up AWS Budgets + Alerts
• Use Cost Explorer daily/weekly
• Apply resource tags for cost allocation

8. Not Using Auto Scaling

Problem:
Fixed number of EC2s serving variable traffic

Result:

• Wasted cost during low traffic
• Poor performance during peak traffic

Prevention:

• Use Auto Scaling Groups (ASG)
• Combine with ALB for load balancing
• Set scaling policies (CPU, latency)

9. Deploying in a Single AZ

Problem:
Hosting app resources in a single availability zone (AZ)

Result:
If that AZ goes down, your app does too.

Prevention:

• Use multi-AZ deployments (e.g., RDS, EC2)
• Use S3 + CloudFront for global distribution
• Replicate stateful resources across regions (if needed)

10. Not Backing Up Critical Data

Problem:
No scheduled backups for databases, file storage, or EBS volumes

Result:
Permanent data loss in case of accidental deletion or corruption

Prevention:

• Use AWS Backup or snapshot automation
• Store backups in separate region or Glacier
• Test backup restoration procedures

11. Manual Deployments Without CI/CD

Problem:
Uploading files via SSH or manually configuring infra

Risks:

• Human error
• No rollback
• Hard to audit

Prevention:

• Use GitHub Actions, CodePipeline, or Jenkins
• Apply Infrastructure as Code (CloudFormation/Terraform)
• Use version-controlled deployment configs

12. No Disaster Recovery Plan

Problem:
No plan for region failure, corrupted DBs, or lost services

Risk:
High downtime and data loss

Prevention:

• Create DR architecture (pilot light, warm standby, multi-site)
• Use Route 53 failover
• Automate backups and infrastructure templates

Summary Table