AWS VPC, Subnets, and Security Groups
Go deep on AWS VPC, Subnets, and Security Groups: edge cases, scalability limits, and how you'd evolve the solution over 2 years.
Answers use simple, clear English.
Audio N/AQuick interview answer
VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless.
Detailed answer
VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless. Private workloads without public IPs. Scale limits often appear in: Misconfigured routes cause outages.. Evolution levers: Least privilege SG; VPC endpoints for S3/ECR; flow logs.. Anchor example: ALB in public subnets; ECS tasks in private; NAT for egress. 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: Tech Lead.
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
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