Final answer:
Two mechanisms that can be used to decouple the voting application from the back-end services that tally the votes are Amazon Simple Queue Service (Amazon SQS) and Amazon Simple Notification Service (Amazon SNS). SQS allows the application to send votes as messages to a queue, while SNS enables real-time communication through the use of topics and subscriptions. Both options provide scalable solutions for handling high volumes of votes in a short timespan.
Step-by-step explanation:
One mechanism that can be used to decouple the voting application from the back-end services that tally the votes is Amazon Simple Queue Service (Amazon SQS). SQS is a fully managed message queuing service that enables you to decouple and scale microservices, distributed systems, and serverless applications.
By using SQS, the voting application can send the votes as messages to a queue, and the back-end services can retrieve and process these messages at their own pace. This decoupling ensures that the voting application doesn't have to wait for the back-end services to process the votes, and can handle the high load of millions of votes within a short timespan.
Another option that may be suitable is Amazon Simple Notification Service (Amazon SNS). SNS is a highly available, durable, and fully managed pub/sub messaging service that allows you to build distributed systems and event-driven architectures. With SNS, the voting application can publish the votes to a topic, and the back-end services can subscribe to this topic and receive the votes in real-time. This allows for near-instantaneous communication between the voting application and the back-end services.