Stepping into the Amazon Web Services (AWS) ecosystem for the first time feels like being handed the keys to a Ferrari. It's powerful, fast, and can take you anywhere. But if you don't know where the brakes are, you're likely to crash—either into a security breach or a $3,000 "surprise" bill at the end of the month.
When I first started with AWS, I thought "Free Tier" meant everything was free. I learned the hard way that a single misconfigured NAT Gateway could cost more than my monthly rent.
To save you from the "Cloud Panic," I've compiled the seven most common mistakes beginners make and how to fix them before they become disasters.
1. Using the Root Account for Daily Tasks
The most common (and dangerous) mistake is logging into the AWS Console using the email address you signed up with and using it for everything.
The Mistake:
The Root User has ultimate power. If those credentials are leaked, a hacker can delete your entire infrastructure, steal data, and even lock you out of your own account.
The "Oops" Moment:
You hardcode your Root access keys into a script, push it to a public GitHub repo, and within minutes, bots are spinning up $10,000 worth of Bitcoin mining instances in 15 different regions.
How to Avoid It:
- Enable Multi-Factor Authentication (MFA) on your Root account immediately.
- Create an IAM User (Identity and Access Management) with administrative permissions for your daily work.
- Lock the Root credentials away and only use them for billing or account-level changes.
💡 Tip:
Check out the AWS IAM Best Practices guide to set up your account securely from Day 1.
2. Leaving S3 Buckets Public
AWS Simple Storage Service (S3) is incredibly easy to use, which makes it incredibly easy to mess up.
The Mistake:
Setting a bucket to "Public" because you want to see if your static website image is working, and then forgetting to turn it off.
The Correct Way:
Keep buckets private by default. Use CloudFront (Content Delivery Network) to serve images or use S3 Pre-signed URLs if you need to give temporary access to a file.
Visual Comparison:
❌ Wrong: Setting S3 Bucket Policy to "Principal": "*" and "Action": "s3:GetObject".
✅ Right: Enabling "Block Public Access" at the account level and using IAM roles for access.
3. The "AdministratorAccess" Trap (IAM Confusion)
When a service doesn't work, beginners often get frustrated and grant that user or service AdministratorAccess just to "make it work."
The Mistake:
Violating the Principle of Least Privilege (PoLP). You give a Lambda function full admin rights when it only needs to read one specific file from one S3 bucket.
How to Avoid It:
Use the AWS Policy Generator to create specific, narrowed-down policies. If a function only needs to write to DynamoDB, only give it dynamodb:PutItem.
4. Ignoring the AWS Free Tier Limits
"Free Tier" does not mean "Unlimited."
The Mistake:
Thinking all services are free. Some services (like Amazon SageMaker or certain NAT Gateways) have no free tier. Others, like EC2, only give you 750 hours a month—which is enough for one instance running 24/7. If you run two instances, you'll start paying halfway through the month.
Real-Life Story:
I once left a t3.medium instance running over a weekend to "test things." It wasn't in the free tier. I came back Monday to a $40 charge for a project that was doing absolutely nothing.
How to Avoid It:
Set up AWS Budgets. Create a budget that emails you the second your forecasted spend hits $1.00.
5. Hardcoding Credentials in Code
This is the "Golden Rule" of Cloud Security: Never put Access Keys or Secret Keys in your code.
The Mistake:
# NEVER DO THIS
aws_access_key = "AKIAIOSFODNN7EXAMPLE"
aws_secret_key = "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"The Correct Way:
Use IAM Roles. If your code is running on an EC2 instance or a Lambda function, attach a "Role" to the resource. AWS will automatically manage the temporary credentials for you.
🔧 Tool Tip:
Use git-secrets or TruffleHog to scan your local repo for secrets before you commit them to GitHub.
6. Not Deleting Resources (The Zombie Infrastructure)
In AWS, you pay for what you provision, not just what you use.
The Mistake:
Terminating an EC2 instance but forgetting to delete the EBS Volume (the hard drive) or the Elastic IP associated with it. AWS charges you for unattached Elastic IPs to prevent IP address wasting.
How to Avoid It:
Always check your "Resources" dashboard. When you delete a project, ensure you check for:
- EBS Snapshots
- Elastic Load Balancers (ELB)
- Unused Elastic IPs
- NAT Gateways (These are surprisingly expensive!)
7. Putting Everything in a Public Subnet
Beginners often put their databases and backend servers in a Public Subnet because it's easier to connect to them via SSH.
The Mistake:
Exposing your Database (RDS) to the open internet. This is an open invitation for brute-force attacks.
The Correct Way:
- Public Subnet: Only for Load Balancers or Bastion Hosts.
- Private Subnet: For your Databases and Application Servers.
How to Connect:
Use AWS Systems Manager (SSM) Session Manager. It allows you to log into your instances without needing an open SSH port (Port 22) or a public IP.
Best Practices Checklist for Beginners
To wrap up, here is your "Pre-Flight Checklist" before you launch anything on AWS:
- ✓MFA is enabled on the Root account.
- ✓AWS Budgets are set to alert me at $5.
- ✓I am using an IAM User, not Root.
- ✓My S3 buckets have "Block Public Access" turned on.
- ✓I have checked which Region I am in (Staying in one region avoids data transfer costs!).
- ✓I am using IAM Roles instead of Access Keys in my code.
Final Thoughts
AWS is a professional-grade tool. While it can be intimidating, avoiding these common pitfalls puts you ahead of 90% of other beginners. Don't be afraid to experiment, but always keep one eye on the Cost Explorer and the other on your Security Hub.
Did you make one of these mistakes? Don't worry—we've all been there. Drop a comment below and share your "AWS Horror Story" so we can all learn together!