AWS S3 and EC2 Interview Questions 2026, 32 Q&A on Storage and Compute
What changed in 2026 drives
Mass-recruiter offer letters are flatter for 2026 batch - the 4-5 LPA ASE band has barely budged in three years while inflation eats real wages. Premium tracks (Digital, Pro, Elite, Specialist) are still where the differential lives, and they are entirely test-driven. If you are aiming higher than the default offer, the coding round is not optional pageantry - it is the entire interview.
What I'd actually study for this
- 01Two solid coding-round answers (1 medium-hard DSA each, with edge-case discussion) > five half-baked ones
- 02One real project you can defend end-to-end - file paths, design decisions, and what you would change
- 03One DBMS schema you actually built (not a textbook ER diagram), with at least 3 join-heavy queries written from memory
- 04Three behavioural STAR stories: failure recovered, conflict handled, ownership taken
Where most candidates trip up
The single biggest mistake is treating company-specific guides as primary prep and DSA as secondary. It is the opposite. Mass recruiters use the test as a filter, but premium tracks at every IT services company use coding to allocate offer band. Spend 70% of prep time on DSA + system fundamentals, 20% on company-specific patterns, 10% on HR rehearsal. Reverse that ratio and you collect the default offer.
Editorial commentary by Aditya Sharma · written for PapersAdda · not generated, not aggregated.
S3 and EC2 are the foundations of AWS, and candidates report they appear in nearly every cloud interview. The questions probe storage classes, bucket security, instance selection, EBS, and pricing models. This guide compiles 32 questions from candidate-reported rounds and public preparation resources, each with detail and the trade-off being tested.
Why these two: almost every AWS architecture stores objects in S3 and runs compute on EC2 (or a layer above it). Mastering both is non-negotiable.
Related: AWS Scenario Based Interview Questions 2026 | AWS Lambda Interview Questions 2026 | Terraform Interview Questions 2026 | Kubernetes Architecture Interview Questions 2026
S3 Storage (Q1 to Q16)
Q1. What is S3 and what are its core concepts?
Q2. What are the S3 storage classes?
| Class | Use case | Retrieval |
|---|---|---|
| Standard | Frequent access | Instant |
| Intelligent-Tiering | Unknown patterns | Instant |
| Standard-IA | Infrequent access | Instant |
| One Zone-IA | Non-critical infrequent | Instant |
| Glacier Instant | Archive, fast | Instant |
| Glacier Flexible | Archive | Minutes to hours |
| Glacier Deep Archive | Long-term compliance | Hours |
Intelligent-Tiering auto-moves objects between tiers based on access. Candidate-reported as a core question.
Q3. How do you secure an S3 bucket?
Q4. What is the difference between a bucket policy and an IAM policy?
Q5. How do you encrypt data in S3?
Q6. What is S3 versioning?
Q7. What are S3 lifecycle policies?
Q8. What is S3 Object Lock?
Q9. How does S3 achieve consistency?
Q10. What is a presigned URL?
Q11. How do you host a static website on S3?
Q12. What is S3 Transfer Acceleration?
Q13. How do you optimize S3 performance for high request rates?
Q14. What is multipart upload?
Q15. How do you replicate S3 data across Regions?
Q16. What causes S3 Access Denied and how do you debug it?
EC2 Compute (Q17 to Q32)
Q17. What is EC2 and what are instance families?
Q18. What is the difference between EBS and instance store?
| EBS | Instance store | |
|---|---|---|
| Persistence | Survives stop/terminate (if not deleted) | Ephemeral, lost on stop |
| Type | Network block storage | Physically attached |
| Use | Databases, OS disks | Scratch, cache |
Instance store is fast but temporary; EBS persists. Candidate-reported as a common question.
Q19. What are the EBS volume types?
Q20. What is an AMI?
Q21. What is the difference between stopping and terminating an instance?
Q22. What is a security group and how does it differ from a NACL?
Q23. What is an Elastic IP and when do you use it?
Q24. What are placement groups?
Q25. What is the difference between On-Demand, Reserved, Spot, and Savings Plans?
| Model | Best for | Saving |
|---|---|---|
| On-Demand | Short, unpredictable | None |
| Reserved | Steady 1 or 3 year usage | High |
| Spot | Interruption-tolerant batch | Highest |
| Savings Plans | Flexible commitment | High |
Spot offers the deepest discount but can be reclaimed; Savings Plans are flexible across instance types. Candidate-reported as a cost question.
Q26. How does Auto Scaling work?
Q27. What is user data and instance metadata?
Q28. How do you give an EC2 instance permissions to AWS services?
Q29. What is the difference between a public and private subnet for EC2?
Q30. How do you patch and maintain EC2 fleets?
Q31. Scenario: an EC2 instance is unreachable over SSH. Diagnose.
Q32. How do you cost-optimize an EC2 workload?
AWS S3 and EC2 Mock Test, 2026 Edition
5 original questions calibrated to the 2026 cloud batch by Aditya Sharma, from candidate-reported patterns.
Question 1
Instance store data is:
a) persistent b) ephemeral, lost on stop c) backed up automatically d) network storage
Solution: Instance store is temporary; use EBS to persist. Answer: (b)
Question 2
A security group is:
a) stateless subnet firewall b) a stateful instance-level firewall c) an IAM policy d) a NACL
Solution: Security groups are stateful and instance-level. Answer: (b)
Question 3
The deepest EC2 discount for interruption-tolerant work is:
a) On-Demand b) Spot c) Reserved d) Savings Plan
Solution: Spot is cheapest but can be reclaimed. Answer: (b)
Question 4
The preferred way to serve an S3 static site is:
a) public bucket b) CloudFront with Origin Access Control, bucket private c) presigned URLs d) FTP
Solution: CloudFront keeps the bucket private and adds TLS/caching. Answer: (b)
Question 5
S3 read-after-write consistency is:
a) eventual b) strong for all operations c) only in one Region d) only for new objects
Solution: S3 provides strong consistency for reads and writes. Answer: (b)
FAQ, AWS S3 and EC2 Questions
Q: How deep are storage classes tested? Candidate-reported rounds expect the access-pattern-to-class mapping and lifecycle automation.
Q: Do freshers get EC2 pricing questions? Yes, the On-Demand vs Spot vs Reserved basics. Placement groups and deep cost work skew experienced.
Q: SSH or Session Manager for access? Session Manager is preferred (no open port 22, audited). Confirm the company's access policy on its docs.
Q: What is the most-missed S3/EC2 concept? S3 access-denied layering and EBS vs instance-store persistence, per candidate-reported feedback.
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Methodology applied to this articlelast verified 8 Jun 2026
- No fabricated salary numbers or success rates. If we quote a range, it's sourced.
- No noun-substituted templates. This article was not generated by swapping company names in a stock prompt.
- No paid placements, sponsored coaching links, or affiliate-shilled course pushes.
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