10 AWS S3 Scenario-Based Questions That Will Stump Even Experts!

AWS S3 is the backbone of cloud storage, yet many underestimate its complexities in real-world scenarios. Whether you’re preparing for an AWS interview or looking to sharpen your skills, these S3 scenario-based questions will test your understanding beyond the basics!

Photo by Maranda Vandergriff on Unsplash

1. Your S3 Bucket is Publicly Accessible — But You Set It to Private

Scenario:

You created an S3 bucket and explicitly denied public access. Yet, when testing with curl, the files are still accessible without authentication.

Question:

What could be causing this, and how do you fix it?

Answer:

• The bucket policy might still allow public access.
• Objects could have an ACL (x-amz-acl: public-read).
• CloudFront or a presigned URL might be exposing the data.
• Fix: Use Block Public Access, audit bucket policies, and check object-level ACLs.

2. S3 Data Disappears — Even With Versioning Enabled

Scenario:

You enabled versioning on an S3 bucket, yet files seem to be deleted permanently.

Question:

How can objects disappear despite versioning?

Answer:

• If Lifecycle Rules are misconfigured, objects can be permanently deleted.
• Users might be using Delete Marker to hide objects, making it seem like they are gone.
• If s3:BypassGovernanceRetention permission exists, objects can still be removed permanently.

Fix: Audit lifecycle rules, check delete markers, and ensure permissions restrict full deletions.

3. 403 Forbidden Error — Even With Proper IAM Permissions

Scenario:

A developer tries to upload a file to an S3 bucket but gets a 403 Forbidden error. Their IAM policy allows full access.

Question:

Why would this happen, and how do you resolve it?

Answer:

• The bucket policy might explicitly deny access (explicit denies override IAM permissions).
• S3 Block Public Access settings might prevent uploads.
• The IAM role might not have s3:PutObjectAcl.
• MFA Delete might be enabled, requiring MFA for deletion.

Fix: Check bucket policies, IAM permissions, and use aws s3api get-bucket-policy to debug.

4. How Do You Prevent Accidental Data Deletion?

Scenario:

A developer accidentally deleted a production dataset in S3. How do you prevent this in the future?

Question:

What AWS features help prevent accidental deletions?

Answer:

• Enable S3 Versioning to recover deleted objects.
• Use MFA Delete to require multi-factor authentication for deletion.
• Apply S3 Object Lock to enforce write-once, read-many (WORM).
• Implement S3 Lifecycle Policies for automatic backups.

5. S3 Costs Skyrocketed Overnight! What Went Wrong?

Scenario:

Your AWS bill suddenly shows massive S3 charges. Usage analysis reveals a spike in PUT requests and data transfer out.

Question:

How do you diagnose and mitigate unexpected S3 costs?

Answer:

• Enable S3 Server Access Logs and analyze request patterns.
• Use AWS Cost Explorer to track API calls and data transfers.
• Implement Intelligent-Tiering to move rarely accessed objects to cheaper storage.
• Use S3 Object Expiration to delete unnecessary data automatically.

6. Cross-Region Replication Fails — But IAM and Policies Are Correct

Scenario:

You set up Cross-Region Replication (CRR) between two buckets. The replication rule is correct, and IAM policies allow replication, but no objects are being copied.

Question:

What might be preventing CRR from working?

Answer:

• Versioning must be enabled on both source and destination buckets.
• Objects uploaded before replication was enabled won’t be replicated.
• The destination bucket lacks ownership permissions (use bucket owner enforced settings).
• Check S3 Replication Metrics for errors.

7. You Can List Files, But Can’t Download Them

Scenario:

Your application can list objects in S3 but fails when trying to download them.

Question:

What could cause this behavior?

Answer:

• IAM policies may allow s3:ListBucket but not s3:GetObject.
• The bucket policy may restrict cross-account access.
• KMS encryption might require extra permissions (kms:Decrypt).

8. S3 Static Website Throws 403 Forbidden

Scenario:

You set up an S3 static website, but it throws a 403 Forbidden error when accessed via the browser.

Question:

How do you troubleshoot and fix this?

Answer:

• The bucket policy might not allow s3:GetObject for public-read.
• The index.html might be missing or misconfigured.
• CloudFront restrictions might be blocking access (check Origin Access Control).

9. How Do You Secure an S3 Bucket That Serves Public Content?

Scenario:

You need to host a public website on S3 but keep files secure from unauthorized modifications.

Question:

What’s the best approach to balance security and accessibility?

Answer:

• Use S3 Signed URLs to restrict access.
• Serve content via CloudFront with Origin Access Control (OAC).
• Enable S3 Object Lock to prevent modification.
• Set up AWS WAF to protect against unwanted requests.

10. Automating S3 Backups to Another AWS Account

Scenario:

Your company requires all critical S3 data to be backed up in a different AWS account automatically.

Question:

What’s the best approach to automate this backup securely?

Answer:

• Use S3 Cross-Account Replication with an IAM role.
• Implement S3 Event Notifications with AWS Lambda to trigger backups.
• Encrypt data using SSE-KMS and allow decryption only for backup accounts.

Final Thoughts

AWS S3 seems simple at first glance, but real-world scenarios reveal hidden complexities. Whether you’re prepping for an AWS interview or improving cloud security, mastering these scenario-based questions will set you apart.

Connect with Me on LinkedIn

Thank you for reading! If you found these DevOps insights helpful and would like to stay connected, feel free to follow me on LinkedIn. I regularly share content on DevOps best practices, interview preparation, and career development. Let’s connect and grow together in the world of DevOps!