AWS Certified Solutions Architect – Associate (SAA-C03)Design Resilient ArchitecturesMedium
A healthcare provider is migrating a legacy on-premises application to AWS. The application uses a monolithic architecture and is sensitive to network latency. The provider needs to ensure that the application remains highly available and fault-tolerant across multiple Availability Zones, with the ability to quickly recover from an AZ outage without re-architecting the application significantly. Which AWS networking component is crucial for enabling this seamless multi-AZ deployment and rapid failover?
- AAmazon VPC Endpoints for private access to AWS services.
- BAn Application Load Balancer (ALB) across multiple AZs.
- CAWS Transit Gateway for inter-VPC connectivity.
- DAmazon Route 53 with simple routing policy.
Show answer & explanationAnswer & explanation
Correct answer: B. An Application Load Balancer (ALB) across multiple AZs.
An Application Load Balancer (ALB) deployed across multiple Availability Zones is crucial for achieving high availability and fault tolerance for a monolithic application. It distributes incoming traffic to healthy targets in different AZs and automatically routes traffic away from unhealthy instances or AZs, enabling rapid recovery without application re-architecture.
Why the other options are wrong
- A. VPC Endpoints provide private access to AWS services, which is a security and networking feature, not a high availability mechanism for applications.
- C. AWS Transit Gateway is for connecting multiple VPCs and on-premises networks, not for load balancing an application across AZs.
- D. Route 53 with simple routing does not perform health checks or direct traffic away from unhealthy instances/AZs for an application.
Application Load Balancer (ALB)
An AWS Elastic Load Balancing (ELB) option that operates at the application layer (Layer 7) and allows for flexible application management and traffic routing to targets in multiple Availability Zones.
- Distributes traffic across multiple targets (EC2, containers, Lambda).
- Performs health checks and routes traffic only to healthy targets.
- Supports path-based, host-based, and query string-based routing.
Memory trick: ALB is the smart traffic cop, directing cars around broken roads.