Building a Production-Grade 3-Tier AWS Architecture with Terraform: Design Decisions, Trade-offs, and Lessons Learned

Short summary

A production-grade 4-tier AWS VPC architecture splits traditional private subnets into frontend and backend layers to limit blast radius if a tier is compromised. The article details network topology, internal load balancing for each tier, secrets management via AWS Secrets Manager with IAM-scoped access, and keyless SSH via SSM Session Manager. Full Terraform source and cost trade-off analysis provided in open-source repo.

• •4-tier VPC (public, frontend private, backend private, database isolated) enforces strict security boundaries instead of collapsing concerns
• •Internal ALBs per tier trade ~$16–20/month for horizontal scaling consistency and independent instance replacement
• •Secrets fetched at boot from Secrets Manager; IAM instance profiles grant only GetSecretValue, no plaintext in code or state

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