Build the deterministic harness around external and machine learning services: request orchestration and batching, strict validation of inbound and outbound payloads, timeouts and retry policy, caching and deduplication, concurrency limits, cost and latency budgets, and defined behavior when a dependency degrades or disappears. Substantial hands-on experience with a major public cloud (AWS or Azure preferred) including serverless compute, containers, managed relational databases, caching, secrets management, identity and access management, and infrastructure as code.