AWS VPC, Subnets, and Security Groups
As a Engineering Manager engineer, explain AWS VPC, Subnets, and Security Groups. What problem does it solve and how would you describe it in an interview?
Answers use simple, clear English.
Quick interview answer
At Engineering Manager depth: start with the problem, then mechanism, then a short example. VPC CIDR, public/private subnets, IGW/NAT, route tables.
Detailed answer
At Engineering Manager depth: start with the problem, then mechanism, then a short example. VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless. Private workloads without public IPs. 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: Engineering Manager.
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?