AWS VPC, Subnets, and Security Groups
Give a real production-style example of using AWS VPC, Subnets, and Security Groups. Walk through the scenario end-to-end.
Answers use simple, clear English.
Quick interview answer
Scenario: ALB in public subnets; ECS tasks in private; NAT for egress. Implementation notes: Least privilege SG; VPC endpoints for S3/ECR; flow logs.
Detailed answer
Scenario: ALB in public subnets; ECS tasks in private; NAT for egress. Implementation notes: Least privilege SG; VPC endpoints for S3/ECR; flow logs. Core: VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless. Private workloads without public IPs. Real-time example: ALB in public subnets; ECS tasks in private; NAT for egress. Pros: Strong network isolation primitives. Cons: Misconfigured routes cause outages. Common mistakes: 0.0.0.0/0 on SSH SG; databases in public subnets. Best practices: Least privilege SG; VPC endpoints for S3/ECR; flow logs. Audience level: Senior.
Full explanation
VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless. Private workloads without public IPs.
Real example & use case
ALB in public subnets; ECS tasks in private; NAT for egress.
Pros & cons
Pros: Strong network isolation primitives. Cons: Misconfigured routes cause outages.
Common mistakes
0.0.0.0/0 on SSH SG; databases in public subnets.
Best practices
Least privilege SG; VPC endpoints for S3/ECR; flow logs.
Follow-up questions
- How would you test AWS VPC, Subnets, and Security Groups?
- What metrics prove AWS VPC, Subnets, and Security Groups is healthy in prod?
- How does AWS VPC, Subnets, and Security Groups change at 10× traffic?