1️⃣ AWS Lambda
Beginner
Q1: What is Lambda?
Lambda is a serverless compute service that runs code in response to events without managing servers. AWS handles provisioning, scaling, patching, and availability.
Q2: When would you use Lambda?
For event-driven workloads like S3 uploads, API Gateway triggers, scheduled jobs, stream processing, and lightweight microservices.
Intermediate
Q3: How does Lambda scale?
Lambda scales automatically by creating concurrent execution environments per request. Each request can trigger a new instance. Concurrency limits apply per region.
Q4: What is cold start?
Cold start occurs when Lambda initializes a new execution environment. It includes runtime startup and code initialization. It is higher in VPC-enabled Lambdas.
Q5: How do you secure Lambda?
Using IAM execution roles, resource-based policies, environment variable encryption (KMS), VPC security groups, and least privilege access.
Advanced
Q6: How do you share files between Lambda instances?
Using EFS (Elastic File System) mounted to Lambda.
Q7: How do you reduce cold start?
Provisioned Concurrency, keeping package small, avoiding VPC unless needed, and using lighter runtimes.
2️⃣ EFS (Elastic File System)
Beginner
Q1: What is EFS?
EFS is a managed NFS file system for Linux workloads that can be mounted to multiple EC2 or Lambda instances simultaneously.
Intermediate
Q2: Difference between EFS and EBS?
| EFS | EBS |
|---|---|
| Shared | Single instance (by default) |
| NFS-based | Block storage |
| Scales automatically | Fixed size |
Advanced
Q3: When would you use EFS with Lambda?
When application needs shared state, large ML models, or persistent file storage across executions.
3️⃣ S3
Beginner
Q1: What is S3?
Object storage service for storing files with high durability (11 9’s).
Q2: What are storage classes?
Standard, IA, Glacier, Intelligent-Tiering.
Intermediate
Q3: What is S3 versioning?
Keeps multiple versions of an object to prevent accidental deletion.
Q4: What is pre-signed URL?
Temporary access to private S3 object.
Advanced
Q5: How do you encrypt S3 data?
- SSE-S3
- SSE-KMS
- Client-side encryption
4️⃣ EBS
Q1: What is EBS?
Block storage attached to EC2.
Q2: Can you attach EBS to multiple instances?
Only Multi-Attach volumes (io1/io2), otherwise single instance.
Q3: How do you back up EBS?
Using EBS snapshots stored in S3.
5️⃣ RDS
Beginner
Q1: What is RDS?
Managed relational database service (MySQL, PostgreSQL, etc.)
Intermediate
Q2: What is Multi-AZ?
Standby replica in another Availability Zone for failover.
Q3: What is Read Replica?
Used for scaling reads.
Advanced
Q4: How do you rotate database credentials securely?
Using AWS Secrets Manager + IAM.
6️⃣ MongoDB
Q1: SQL vs MongoDB?
SQL = relational, fixed schema.
MongoDB = NoSQL, document-based, flexible schema.
Q2: What is sharding?
Horizontal scaling by distributing data across nodes.
7️⃣ CloudFront
Beginner
Q1: What is CloudFront?
Content Delivery Network (CDN) to cache content globally.
Intermediate
Q2: What is edge location?
Physical data center location where content is cached.
Advanced
Q3: How does CloudFront improve security?
WAF integration, signed URLs, OAC/OAI for S3, HTTPS.
8️⃣ Global Accelerator
Beginner
Q1: What is Global Accelerator?
Improves availability and performance using AWS global network.
Advanced
Q2: Difference between CloudFront and Global Accelerator?
| CloudFront | Global Accelerator |
|---|---|
| CDN | TCP/UDP accelerator |
| Caches content | Does not cache |
| HTTP/HTTPS | Any TCP/UDP |
9️⃣ EC2
Q1: What is EC2?
Virtual machine in AWS.
Q2: What is Auto Scaling Group?
Automatically adjusts EC2 capacity.
Q3: What is Launch Template?
Template defining instance configuration.
🔟 Security Groups
Q1: What is Security Group?
Stateful firewall attached to EC2.
Q2: Stateful vs Stateless?
SG = Stateful
NACL = Stateless
1️⃣1️⃣ API Gateway
Q1: What is API Gateway?
Managed service to create REST/HTTP/WebSocket APIs.
Q2: How does it integrate with Lambda?
Triggers Lambda via proxy integration.
1️⃣2️⃣ Serverless Architecture
Q1: What is serverless?
No server management, event-driven, pay-per-use.
Senior Answer:
Serverless is operational abstraction. AWS manages infrastructure while we focus on code and business logic.
1️⃣3️⃣ Edge Location
Edge location is a data center used by CloudFront and Route53 for low-latency response.
1️⃣4️⃣ KMS & SSE-KMS
KMS
AWS Key Management Service manages encryption keys.
SSE-KMS
Server-side encryption using KMS-managed keys.
Difference SSE-S3 vs SSE-KMS?
- SSE-S3 → AWS-managed key
- SSE-KMS → Customer-controlled key + audit trail (CloudTrail)
1️⃣5️⃣ IAM
Beginner
What is IAM?
Identity and Access Management.
Intermediate
What is least privilege?
Grant minimum permissions required.
Advanced
Explain IAM Role vs Policy?
Policy = permission document.
Role = identity that can be assumed.
🔥 Architect-Level Scenario Question
Design a secure serverless image processing system.
Answer structure:
Client → API Gateway → Lambda → S3
S3 → Event → Worker Lambda → Store processed image
CloudFront → Serve content globally
KMS → Encrypt data
IAM → Least privilege
Global Accelerator → Multi-region resilience
RDS/MongoDB → Metadata storage
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