# The Azure Well-Architected Framework — Azure

Source: https://www.skillbyai.com/en/azure/p-waf

> Review an Azure design against the five Well-Architected pillars.

## Five pillars for design reviews

Microsoft's **Azure Well-Architected Framework** organises design guidance into five pillars. **Reliability**: zones, multi-region where needed, health probes, retries, backups and tested recovery. **Security**: identity first, least privilege, private networking, encryption, secrets in Key Vault. **Cost Optimization**: right-sizing, autoscale, commitments, tags and budgets. **Operational Excellence**: infrastructure as code, CI/CD, observability and safe deployment practices. **Performance Efficiency**: choosing the right service and tier, scaling out, caching and load testing. The pillars trade off against each other: multi-region active-active improves reliability but costs more. Also understand **SLAs**: if a request depends on two services in series, the composite availability is roughly the product, so 99.95% × 99.99% ≈ 99.94%, lower than either one.

## A reference shape for a small production web app

A common starting point that touches every pillar.

```text
users
  -> Azure Front Door (WAF, TLS, global routing, caching)
    -> App Service or Container Apps (2+ instances, zone redundant, autoscale)
         | managed identity
         +-> Azure SQL / PostgreSQL Flexible (zone-redundant HA, PITR backups)
         +-> Storage account (ZRS, private endpoint, lifecycle rules)
         +-> Key Vault (RBAC, purge protection) via Key Vault references
         +-> Service Bus (async work, dead-letter queue) -> Functions worker
  observability: Application Insights + Log Analytics, alerts on errors/latency
  delivery:      Bicep + GitHub Actions (OIDC, what-if, approvals)
  guardrails:    Azure Policy at management group, Defender for Cloud, budgets
```

## Write down the trade-off

In interviews and design reviews, saying *why* you rejected the more reliable or cheaper option matters as much as the final diagram. Name the requirement that drove the decision.

**Quiz:** A request flows through two services in series with SLAs of 99.95% and 99.99%. What is the approximate composite availability?

- [x] About 99.94%
- [ ] 99.99%
- [ ] 99.95%
- [ ] 100%

*Answer:* About 99.94%. For dependencies in series, multiply the availabilities: 0.9995 × 0.9999 ≈ 0.9994.