In Kubernetes, node heartbeats are implemented through Lease objects in the coordination.k8s.io API group. By default, each node updates its Lease every 10 seconds to signal liveness.

For example, in a 5,000-node cluster, this results in:
- 500 write operations per second (5,000 nodes ÷ 10 seconds)
- 500 read operations per second (as controllers check these leases)

This sustained load on etcd creates significant:
- Write amplification from frequent small updates
- Storage overhead from maintaining revision history
- Network traffic between etcd members

These factors make etcd a scaling bottleneck for large clusters, particularly for this high-frequency, low-value coordination data.