Fivetran engineers describe their migration from a fragmented, custom-built scheduling system to Temporal for orchestrating over 6 million data syncs per day. The talk covers the legacy architecture's pain points (distributed control loops, Kubernetes API limits, 25-second job startup latency), the phased migration approach (validation benchmarks, gradual rollout, operator implementation for long-running jobs), and the resulting architecture using Temporal Cloud with a worker pool model that reduced startup latency to under 5 seconds. Key technical details include using signal-with-start instead of child workflows to support many-to-one pipeline-to-connector relationships, a custom gRPC gateway for hybrid deployment tenant isolation, namespace splitting, and HPA-based cost optimization. Future plans include adopting Nexus for cross-namespace communication and splitting monolithic activities into composable units.