Answer
The application controller can run multiple replicas, each assigned a shard of clusters (by a sharding algorithm). This spreads reconciliation work so no single controller is overloaded managing hundreds of clusters, improving throughput and resilience at scale.
env:
- name: ARGOCD_CONTROLLER_REPLICAS
value: "3"Real-world example Three controller shards each handle a third of the 300-cluster fleet, keeping reconciliation timely.