Step 2: Architecture Assessment - terraform-e2e

🏛️ Step 2: Architecture Assessment - terraform-e2e

• ✅ Requirements Validation
• 💎 Executive Summary
• 🏛️ WAF Pillar Assessment
• 📦 Resource SKU Recommendations
• 🎯 Architecture Decision Summary
• 🚀 Implementation Handoff
• 🔒 Approval Gate
• References

Generated by architect agent | 2025-07-14

✅ Requirements Validation

[!NOTE] All requirement areas fully defined. Challenger review completed at Step 1 with 7 findings addressed. Network security has a governance validation gate — must check against 04-governance-constraints.json before finalizing.

💎 Executive Summary

This is a small ecommerce storefront for a startup with <100 concurrent users, deployed to Azure as a dev-only environment using Terraform IaC. The architecture follows a Cost-Optimized N-Tier pattern: Static Web App (frontend) → App Service (backend API) → Azure SQL (data store), with Microsoft Entra External ID for customer authentication.

The primary optimization pillar is Cost — all SKUs target the lowest viable tier while maintaining the 99.5% SLA target. Security is adequate for dev but would need private endpoints, WAF, and network isolation before promoting to production. Reliability is deliberately relaxed (RTO 24h, RPO 12h) given the single-region, dev-only posture.

Recommended Architecture

flowchart TB
    User["👤 Customers<br/>< 100 concurrent"] --> SWA["🌐 Static Web App<br/>Free tier · westeurope"]
    Admin["👤 Store Admin"] --> SWA
    SWA --> API["💻 App Service B1<br/>Backend REST API · swedencentral"]
    API --> SQL["💾 Azure SQL Basic<br/>5 DTU · swedencentral"]
    API --> KV["🔑 Key Vault Standard<br/>swedencentral"]
    API --> APPI["📊 Application Insights<br/>swedencentral"]
    User --> EntraEID["👤 Entra External ID<br/>OIDC Auth"]
    EntraEID --> SWA
    APPI --> LOG["📋 Log Analytics<br/>swedencentral"]

    subgraph "Identity"
        EntraEID
    end

    subgraph "Security & Management"
        KV
    end

    subgraph "Data"
        SQL
    end

    subgraph "Monitoring"
        APPI
        LOG
    end

Terraform-Specific Notes

• State management: Remote state in Azure Blob Storage backend with state locking
• Provider: azurerm ~> 4.0 with hashicorp/random for unique suffixes
• AVM-TF modules: Available for App Service, SQL Server, Key Vault, Log Analytics, App Insights
• Static Web App: No AVM-TF module confirmed — may require raw azurerm_static_web_app resource
• Unique suffix: random_string (4 chars, lowercase) replaces Bicep's uniqueString()

🏛️ WAF Pillar Assessment

Overall Scores

Primary Pillar Optimized: 💰 Cost Optimization Trade-offs Accepted: Relaxed reliability (single region, no failover) and security (public endpoints, no WAF) in exchange for minimal cost in dev environment

🔒 Security Assessment (6/10)

Strengths:

• Managed Identity for App Service → Azure SQL connectivity (no credentials in code)
• Key Vault Standard for centralized secret management
• TLS 1.2 enforced on all services; AES-256 encryption at rest
• Microsoft Entra External ID for customer OIDC authentication
• Admin MFA required for Store Admin and Platform Engineer roles
• GDPR controls defined and mapped to Azure features (see table below)

GDPR Control → Azure Feature Mapping:

Legend: ✅ Addressed = infrastructure-level control; ⚠️ App-layer = requires application code implementation in addition to infrastructure

Gaps:

• No private endpoints — all services use public endpoints (accepted for dev)
• No Web Application Firewall (WAF) — low traffic does not justify cost in dev
• No DDoS Protection Standard — Basic DDoS included with Azure platform
• No network isolation (VNet integration or NSGs for App Service)
• No threat detection or Microsoft Defender for Cloud

Recommendations:

1. Before production: Enable private endpoints for SQL and Key Vault; add VNet integration for App Service
2. Before production: Deploy Azure Front Door with WAF policy or App Gateway WAF v2
3. Enable Microsoft Defender for Cloud (Free tier) for security posture visibility
4. Configure Azure SQL auditing and threat detection (included at no extra cost)
5. Validate network controls against subscription governance policies in Step 4

🔄 Reliability Assessment (5/10)

Composite SLA Calculation:

These services are in a serial dependency chain (SWA → App Service → SQL), so the composite SLA is the product:

$$SLA_{composite} = 0.9995 \times 0.9995 \times 0.9999 \times 0.9999 \times 0.9999 \times 0.999 = 0.9977 \approx 99.77%$$

Result: Composite SLA 99.77% exceeds the 99.5% target with a 0.27% margin. Annual downtime budget: ~19.3 hours (target allows ~43.8 hours).

Strengths:

• Composite SLA 99.77% exceeds the 99.5% target requirement
• Azure SQL Basic includes automatic PITR (Point-In-Time Restore) with 5-minute granularity and 7-day retention
• Static Web App provides built-in global CDN and edge availability
• Infrastructure defined as code (Terraform) enables repeatable rebuilds
• Scale-out triggers documented with clear thresholds

Gaps:

• Single region deployment — no geo-redundancy or failover region configured
• No Availability Zones leveraged (B1 App Service Plan does not support AZ)
• No automated health probes or self-healing beyond Azure platform defaults
• RTO 24h depends on manual intervention (Terraform re-apply from scratch)
• SQL Basic tier offers no zone redundancy or read replicas

Recommendations:

1. Accept current posture for dev-only — RTO 24h and RPO 12h are achievable
2. Before production: Upgrade to P1v4 App Service Plan to enable Availability Zones (S1 does not support AZ)
3. Before production: Enable Azure SQL geo-replication to germanywestcentral
4. Configure App Service health check endpoint for automatic instance recycling
5. Document manual recovery procedure (Terraform plan + apply) as interim DR plan

⚡ Performance Assessment (7/10)

Strengths:

• Static Web App serves frontend from global CDN edge — sub-second delivery for static assets
• App Service B1 (1 vCPU, 1.75 GB RAM) adequate for <100 concurrent users and <50 txn/day
• Azure SQL Basic (5 DTU) sufficient for lightweight CRUD operations on <2 GB data
• Application Insights enables end-to-end tracing for latency identification

Gaps:

• No caching layer (Azure Cache for Redis) — all API requests hit SQL directly
• App Service B1 is single-instance, no autoscaling capability
• B1 plan has limited CPU/memory — sustained load above 80 users may degrade performance
• No CDN or Front Door for API acceleration (backend is single-region)

Recommendations:

1. Monitor API p95 latency via Application Insights; target <500ms is achievable at current scale
2. At 80 concurrent users: Evaluate App Service scale-out (upgrade to S1 for autoscale support)
3. At 500+ users: Add Azure Cache for Redis (Basic C0) for session state and frequent queries
4. Configure Application Insights availability tests to measure end-user page load times

💰 Cost Assessment (9/10)

[!WARNING] MCP Pricing Confidence: Medium — App Service B1 price confirmed by azure_bulk_estimate. SQL Database Basic, Application Insights, and Log Analytics were unresolved by MCP tools (SKU name mismatches). Ranges shown are from requirements component guardrails. Key Vault returned incorrect meter ($2,190 — wrong SKU mapping). Actual Key Vault cost for 1000 operations/month is negligible (<$1).

Cost Optimization Applied:

• Free tier selected for Static Web Apps and Entra External ID (within free limits)
• Basic/B1 SKUs selected for compute and database — lowest viable tiers
• Pay-per-GB monitoring with first 5 GB free reduces monitoring costs
• No reserved instances needed at this scale and commitment level
• Consumption-based model preferred per requirements

🔧 Operational Excellence Assessment (6/10)

Strengths:

• Terraform IaC ensures reproducible, version-controlled infrastructure
• Application Insights + Log Analytics provide observability across all deployed resources
• Diagnostic settings enabled for audit logging
• Alert MTTA target <30 minutes achievable with email notifications
• 100% monitoring coverage target with App Insights auto-instrumentation

Gaps:

• No CI/CD pipeline defined (manual Terraform apply)
• No automated testing (infrastructure or application)
• No operations runbooks or playbooks documented
• No automated alerting rules configured yet (will be defined in Step 4/5)
• Maintenance windows defined but not enforced via Azure Maintenance Configurations

Recommendations:

1. Configure GitHub Actions workflow for Terraform plan/apply (can be deferred to post-MVP)
2. Set up basic alert rules: SQL DTU >80%, App Service CPU >80%, HTTP 5xx errors >1%
3. Document manual operations procedures: scale-out, backup restore, incident response
4. Enable Azure Monitor action groups for email notifications to team-terraform

Service Maturity Assessment

[!NOTE] All services are Generally Available with low deprecation risk. Entra External ID is the official successor to Azure AD B2C (end-of-sale May 2025). AVM-TF module for Static Web Apps should be verified during implementation planning (Step 4).

📦 Resource SKU Recommendations

Selected: B1 — lowest always-on tier; sufficient for <100 users. Production AZ path: P1v4 (P1v3 also supports AZ but P1v4 is the latest generation)

Selected: Basic (5 DTU) — adequate for <50 txn/day and <2 GB data; upgrade to S0 if DTU consistently >80%

🎯 Architecture Decision Summary

🚀 Implementation Handoff

Ready for terraform-plan

The architecture is approved for implementation with the following key parameters:

Resources to Provision

[!NOTE] Terraform state backend (Storage Account + Container) is a prerequisite resource that must be provisioned separately before terraform init.

Security Requirements for Implementation

Monitoring Requirements for Implementation

🔒 Approval Gate

[!IMPORTANT] 🏗️ Architecture Assessment Complete

Pillar	Score
🔒 Security	6/10
🔄 Reliability	5/10
⚡ Performance	7/10
💰 Cost Optimization	9/10
🔧 Operational Excellence	6/10

Composite WAF Score: 6.6/10

Estimated Monthly Cost: ~$25–$60 (within $500–$2,000 budget)

Confidence Level: Medium (partial MCP pricing; see cost estimate for details)

Primary optimization: Cost — all SKUs at lowest viable tier for dev-only environment

• Approved — proceed to terraform-plan
• Approver: User
• Date: 2026-02-26

Challenger findings addressed: SEC-003 (GDPR mapping added), REL-001 (SLA math added — 99.77% composite), REL-002 (AZ path corrected to P1v4). SEC-001 and SEC-002 deferred to Step 4 governance discovery.

References

[!NOTE] 📚 The following Microsoft Learn resources informed this assessment.

Assessment performed using Azure Well-Architected Framework. Pricing data from Azure Pricing MCP (2025-07-14). App Service B1 confirmed at $13.14/month; other items partially resolved.