The most appropriate solution is Deploy an Amazon CloudFront distribution that uses the existing ALB as its origin and configure the cache behavior to vary based on the Accept-Language HTTP header. CloudFront is a global content delivery network (CDN) that caches content at edge locations closer to users around the world. By using the Application Load Balancer as the origin, you dont need to replicate infrastructure across Regions. Configuring CloudFront to cache based on the Accept-Language header ensures that language-specific content is served correctly without unnecessary round trips to the backend.

The option Migrate the website content to an S3 bucket and serve it statically via Amazon CloudFront with caching based on language headers is not suitable here. While it would reduce latency, the application is dynamic and relies on backend EC2 instances. Moving the site to static hosting would require re-architecting the solution, which contradicts the goal of avoiding infrastructure changes.

The choice Use Amazon API Gateway to integrate with the ALB using HTTP integration and enable API caching based on the Accept-Language header is a poor fit for a dynamic website. API Gateway is optimized for API-based traffic, not full HTML or web content delivery, and adds unnecessary complexity and cost for a use case better handled by CloudFront.

The option Provision EC2-based caching proxies in each desired Region using NGINX, and configure Route 53 geolocation-based routing to direct users to the nearest cache involves significant overhead and defeats the goal of maintaining a centralized architecture. Managing EC2 instances in each Region increases maintenance burden and cost compared to a fully managed CDN like CloudFront.

This question highlights a core design principle in AWS: global content distribution using managed services like CloudFront to reduce latency and improve user experience without replicating backend systems. A common trick is to identify the keyword "latency" for geographically dispersed users, which often signals the need for CloudFront or another edge-optimized service.

What makes this question tricky is that several options seem viable for improving performance, but only one truly aligns with minimizing architectural changes and operational complexity. CloudFront with header-based caching delivers global acceleration and language-aware behavior with minimal effort and no changes to the existing EC2-based infrastructure.

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