A developer must build a cost-effective proof-of-concept REST endpoint that returns the weather forecast for a company office. The solution should use AWS caching where possible and will only receive light traffic during testing. Which implementation is the most cost-effective?

Using AWS Lambda with Amazon API Gateway is the most cost-effective solution for a light-traffic proof-of-concept. Lambda is a serverless, pay-per-execution service, meaning you only pay when your function is invoked, which is ideal for low usage. API Gateway provides a fully managed, scalable entry point for your REST endpoint, and its free tier covers substantial usage. AWS SAM (Serverless Application Model) simplifies the deployment of Lambda functions and API Gateway. Running containers on Amazon EKS or ECS involves managing underlying infrastructure (even if Fargate is used, there are still operational considerations) and incurs costs even when idle, making them less cost-effective for a low-traffic PoC. Elastic Beanstalk, while simplifying deployment, still runs on EC2 instances, incurring continuous costs.