How would you test AWS VPC, Subnets, and Security Groups?

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Quick interview answer

Test AWS VPC, Subnets, and Security Groups with unit checks for the happy path, integration tests for real I/O boundaries, and load/chaos checks so regressions show up before prod. Core idea: VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless.

Detailed answer

Interview answer for testing AWS VPC, Subnets, and Security Groups: 1) Unit: isolate the pure logic behind AWS VPC, Subnets, and Security Groups with deterministic fixtures. 2) Integration: exercise real timers/I/O/network boundaries the way production does. 3) Load & soak: prove the event path still meets SLOs under concurrency. 4) Failure injection: break dependencies and assert recovery/backpressure. Best practices to include: Least privilege SG; VPC endpoints for S3/ECR; flow logs. Call out mistakes: 0.0.0.0/0 on SSH SG; databases in public subnets. Parent context: VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless.

Full explanation

Interviewers want a test strategy, not “I would write tests.” Tie each layer back to how AWS VPC, Subnets, and Security Groups fails: correctness, latency, and starvation. VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless. Private workloads without public IPs.

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Parent context — AWS VPC, Subnets, and Security Groups

VPC CIDR, public/private subnets, IGW/NAT, route tables. Security groups stateful allow-lists; NACLs stateless.

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