Sync Operation Backlog from Insufficient Controller Concurrency
criticalArgoCD application controller cannot keep up with reconciliation demand when status/operation processor counts are too low for the number of managed applications, causing sync delays and stale application states.
Monitor argocd_app_reconcile queue depth and argocd_app_controller_workqueue_queue_time_seconds. When queue time exceeds 5 minutes or queue depth grows continuously with 100+ applications, controller is under-provisioned. Also check argocd_app_controller_process_cpu_seconds approaching limits.
Scale controller concurrency: increase status processors to ~50 and operation processors to ~25 for 1000 applications (adjust proportionally). Set controller.status.processors and controller.operation.processors via Helm extraArgs. Consider horizontal scaling with multiple controller replicas if workload exceeds single pod capacity.