Highly Available Three-Tier Web Application on AWS
This starter architecture separates ingress, presentation, application logic, and relational data so each tier can fail and scale independently. It is a practical baseline for teams moving a conventional web application onto AWS without collapsing every responsibility into one server.
Published August 18, 2026
Reference architecture
Architecture diagram
Open on the canvasHighly available three-tier AWS architecture diagram with an Application Load Balancer, Auto Scaling web and application tiers, and Amazon RDS Multi-AZ. The image links to a fully editable BuildPlane starter.
Overview
A junior-friendly three-tier web application that stays available when an instance or one Availability Zone fails. The diagram keeps the story focused on resilient ingress, independently scalable compute tiers, and durable relational data.
Components
- Application Load Balancer: Accepts HTTPS traffic, checks target health, and distributes requests across Availability Zones.
- Web Tier: Serves the web experience from a stateless Auto Scaling fleet in private subnets.
- Application Tier: Runs business logic in a separate Auto Scaling fleet so application capacity can change independently.
- RDS Multi-AZ: Stores relational data and maintains a synchronous standby for automatic database failover.
Request Flow
- Web users send HTTPS requests to the Application Load Balancer.
- The load balancer routes healthy traffic to the web tier across two Availability Zones.
- The web tier calls the application tier for business operations.
- The application tier reads and writes relational data in RDS Multi-AZ.
Customize First
- Choose instance sizes and scaling signals for the web and application tiers.
- Add CloudFront and WAF when the application needs global caching and edge protection.
- Add backups, monitoring, and secrets management before production use.
Design rationale
Decisions that shape this architecture
Scale the web and application tiers separately
The web tier and application tier use separate Auto Scaling capacity. A traffic spike that increases page delivery does not have to force the same scaling policy on business logic workers.
Keep compute stateless
Requests can move between healthy instances because session state and durable records do not live on one application host. This is what lets the load balancer remove failed targets safely.
Use Multi-AZ for database availability
RDS Multi-AZ maintains a synchronous standby for failover. It improves availability, but it is not a read-scaling strategy and it does not replace backups.
Before production
Operational checks
Test target health checks against real application readiness, not only process uptime.
Set minimum Auto Scaling capacity in each Availability Zone.
Exercise database reconnection behavior during an RDS failover.
Add alarms for unhealthy targets, scaling saturation, error rate, and database pressure.
Scope and tradeoffs
What this diagram does not solve
One Region remains a shared failure domain
The design handles instance and Availability Zone failures inside one Region. Regional continuity requires a second deployment, data replication, and an explicit traffic failover policy.
Security and operations need workload-specific detail
Security groups, secrets rotation, patching, backups, WAF rules, and deployment controls should be added around the actual application requirements.
Common questions
Frequently asked questions
Why separate the web tier from the application tier?
The separation gives each tier its own scaling, deployment, and failure boundary. It is useful when frontend delivery and application processing have different capacity profiles.
Does RDS Multi-AZ improve read performance?
No. Multi-AZ primarily provides a standby for availability. Add read replicas or another read-scaling design when query volume requires it.
Can I edit this AWS architecture diagram?
Yes. Open the starter in BuildPlane to move services, change boundaries, add controls, and ask the AI Agent to adapt the design to your workload.
Keep exploring
Related AWS architectures
An AWS Application That Survives an Availability Zone Failure
This architecture focuses on one failure question: what happens when an entire Availability Zone becomes unavailable? Healthy application capacity remains in the other zone, the load balancer removes failed targets, and RDS can promote its synchronous standby.
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Production-Grade Highly Available Web Platform on AWS
This reference expands the three-tier baseline with a global edge, separate scaling domains, caching, read scaling, private egress, secrets, backups, and operations. It is intended for teams evaluating a conventional production web platform rather than a minimal learning diagram.
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Public and Private Subnets in an AWS VPC
This VPC pattern makes exposure decisions explicit. The load balancer and NAT gateway live in the public path, application compute accepts traffic only from the load balancer, and the database has no direct route from the internet.
Explore the architectureFrom reference to working draft
Adapt this architecture with your AWS AI Agent
Start from the exact diagram in this guide. Change requirements, challenge a decision, or ask what fails first, while keeping the architecture editable.