Highly available three-tier web application

Highly available three-tier web application Highly available three-tier web application Front Door + WAF → Application Gateway → VM scale sets → Azure SQL Database, across two availability zones Azure Region Resource group Virtual network Availability zone 1 Availability zone 2 App subnet Data subnet App subnet Data subnet HTTPS 1. Users → Azure Front Door (HTTPS)1 2. Azure Front Door → Application Gateway2 SQL 4. VM scale set → Azure SQL Database (SQL)4 4. VM scale set → Azure SQL Database4 inspects sync replication static assets 3. Application Gateway → VM scale set3 3. Application Gateway → VM scale set3 Users (Users) Users Web Application Firewall (Web Application Firewall Policies(WAF)) Web Application Firewall managed rules + bot protection Azure Front Door (Front Door and CDN Profiles) Azure Front Door global entry, caching Azure Storage (Storage Accounts) Azure Storage static assets Application Gateway (Application Gateways) Application Gateway WAF v2, zone-redundant VM scale set (VM Scale Sets) VM scale set web tier Azure SQL Database (SQL Database) Azure SQL Database primary VM scale set (VM Scale Sets) VM scale set web tier Azure SQL Database (SQL Database) Azure SQL Database readable replica Azure Monitor (Monitor) Azure Monitor metrics, logs, alerts Azure Key Vault (Key Vaults) Azure Key Vault

Flow

  1. 1Users → Azure Front Door (HTTPS)
  2. 2Azure Front Door → Application Gateway
  3. 3Application Gateway → VM scale set
  4. 3Application Gateway → VM scale set
  5. 4VM scale set → Azure SQL Database (SQL)
  6. 4VM scale set → Azure SQL Database

Cost estimate eastus · price list as of 2026-10-02 · indicative — some usage is assumed

$1,792per month
$21,498per year
9/11components priced
0not priced (see below)

Public pay-as-you-go list prices from the Azure Retail Prices API (USD). Excludes taxes, support plans, Reservations, Savings Plans, Spot and enterprise or EA discounts, and data transfer unless a node sets egressGbPerMonth. Free grants are included where the meter has a free tier. Monthly = 730 hours. Not a quote: confirm with the Azure Pricing Calculator.

Usage basis. Illustrative: ~2M page views/month, 500 GB edge egress, two D2s v5 web VMs per zone, SQL Database Business Critical 4 vCores (replicas included).

By category

Data and storage$958 · 53%
Network$421 · 23%
Compute$280 · 16%
Security and operations$133 · 7%
Other$0.00 · 0%

By component click a row to highlight it on the diagram

ComponentServiceStatus$ / monthLine items
Azure SQL DatabaseSQL Databaseestimated$951
2 lines
  • Business Critical Gen5 4 vCore hours: 730 1 Hour × $1.2177 = $888.9502
  • Data storage (GB-month): 250 1 GB/Month × $0.25 = $62.50

Provisioned vCore, single database. Excludes backup storage beyond the free allocation, licence benefit and serverless auto-pause.

Application GatewayApplication Gatewaysestimated$294
2 lines
  • Fixed cost (gateway-hours): 730 1/Hour × $0.36 = $262.80
  • Capacity unit-hours: 2,190 1/Hour × $0.0144 = $31.536

WAF v2 SKU; autoscale capacity units assumed constant.

VM scale setVM Scale Setsestimated$140
1 line
  • Standard_D2s_v5 instance-hours (Linux): 1,460 1 Hour × $0.096 = $140.16

Linux pay-as-you-go compute only; excludes OS and data disks, public IPs, networking and Windows/SQL licences.

VM scale setVM Scale Setsestimated$140
1 line
  • Standard_D2s_v5 instance-hours (Linux): 1,460 1 Hour × $0.096 = $140.16

Linux pay-as-you-go compute only; excludes OS and data disks, public IPs, networking and Windows/SQL licences.

Azure MonitorMonitorestimated$127
1 line
  • Data ingestion (GB): 60 1 GB × $0.00 (tiered) = $126.50

Pay-as-you-go ingestion with the monthly free allowance in the tier; commitment tiers are not modelled.

Azure Front DoorFront Door and CDN Profilesestimated$126
4 lines
  • Standard base fee (month): 1 1/Month × $35.00 = $35.00
  • Requests: 2,000 10K × $0.00 = $18.00
  • Edge data transfer out (GB), zone 1: 500 1 GB × $0.00 = $41.25
  • Data transfer out to the internet (GB): 500 1 GB × $0.00 (tiered) = $32.00

Zone 1 (North America and Europe) rates; other zones cost more. Routing-rule overage and WAF custom rules are not modelled.

Azure StorageStorage Accountsestimated$6.66
3 lines
  • Data stored, Hot LRS (GB-month): 200 1 GB/Month × $0.00 = $4.16
  • Write operations: 10 10K × $0.05 = $0.50
  • Read operations: 500 10K × $0.004 = $2.00

Excludes data retrieval and early-deletion charges, egress and transactions on other APIs.

Azure Key VaultKey Vaultsestimated$6.00
1 line
  • Secret and key operations: 200 10K × $0.03 = $6.00

Standard tier software-protected keys; HSM keys and certificates are not modelled.

Not priced

  • Web Application Firewall — no-charge: Web Application Firewall Policies(WAF) has no direct charge.
  • Azure SQL Database — override: Replica is included in the Business Critical price.

Assumptions 9 defaulted — replace them with your own numbers in each node's usage

ComponentAssumptionValueSource
Azure Front Doortierstandardfrom spec
Azure Front DooregressGbPerMonth500from spec
Azure Front DoorrequestsPerMonth20000000from spec
Azure StorageaccessTierhotassumed
Azure StorageredundancyLRSassumed
Azure StoragestorageGb200from spec
Azure StoragewriteOperationsPerMonth100000assumed
Azure StoragereadOperationsPerMonth5000000from spec
Application Gatewaywaftruefrom spec
Application GatewayavgCapacityUnits3from spec
VM scale setvmSizeStandard_D2s_v5from spec
VM scale setcount2from spec
VM scale sethoursPerMonth730assumed
Azure SQL Databasetierbusiness-criticalfrom spec
Azure SQL Databasevcores4from spec
Azure SQL DatabasezoneRedundantfalseassumed
Azure SQL DatabasestorageGb250from spec
Azure SQL DatabasehoursPerMonth730assumed
VM scale setvmSizeStandard_D2s_v5from spec
VM scale setcount2from spec
VM scale sethoursPerMonth730assumed
Azure MonitoringestGbPerMonth60from spec
Azure MonitorretentionDays31assumed
Azure MonitorretainedGb10assumed
Azure Key VaultoperationsPerMonth2000000from spec

Sensitivity & what-if

$1,792at 1× traffic
$2,416at 3× traffic
$4,603at 10× traffic

No what-if options apply to these services.

Price list provenance

Retrieved 2026-10-02T10:01:47.868Z from the public Azure Retail Prices API. Latest price effective dates per service:

Bandwidth 2022-05-01 · Azure Front Door Service 2026-05-01 · Storage 2026-09-01 · Application Gateway 2025-12-01 · Virtual Machines 2026-10-01 · SQL Database 2025-10-01 · Log Analytics 2018-02-01 · Key Vault 2022-03-01

Only public pay-as-you-go list prices are used. This is not a quote — confirm in the Azure Pricing Calculator.