Which architecture is most cost-effective for sporadic, event-driven workloads?

• A. Monolithic
• B. Microservices
• C. Serverless
• D. Client-Server

Answer: (C)

For workloads that happen only occasionally and are triggered by events, the most cost-effective approach is one that charges only for actual work and scales to zero when idle. Serverless fits this pattern perfectly: you write functions that run in response to events, and the cloud provider handles the rest, so you don’t pay for idle compute. You’re billed per invocation and for the execution time used, which means costs rise only when the workload occurs and automatically shrink back to zero when there’s no activity.

Monolithic architectures require provisioning a fixed capacity to handle peak load, so idle time still costs money. Microservices add modularity but involve running multiple services and orchestration layers, which can accumulate costs and complexity—especially if several components stay active to be ready. Client-server is a traditional setup that generally involves keeping servers up and running, again leading to ongoing costs even when demand is low.

Keep in mind serverless can bring challenges like cold starts and limits on long-running tasks, but for sporadic, event-driven workloads, the pay-per-use, auto-scaling nature makes it the most cost-effective choice.