A digital wallet company plans to launch a new cloud-based service for processing user cash transfers and peer-to-peer payments. The application will receive transaction requests from mobile clients via a secure endpoint. Each transaction request must go through a lightweight validation step before being forwarded for backend processing, which includes fraud detection, ledger updates, and notifications. The backend workload is compute- and memory-intensive, requires scaling based on volume, and must run for a longer duration than typical short-lived tasks. The engineering team prefers a fully managed solution that minimizes infrastructure maintenance, including provisioning and patching of virtual machines or containers. Which solution will meet these requirements with the LEAST operational overhead?