The HPA grows and shrinks a Deployment by load
A HorizontalPodAutoscaler is a feedback controller, not a capacity planner. Once every sync period — 15 seconds by default — it asks the resource metrics API for per-pod CPU, divides the observed value by the target to get a ratio, and writes the result into the target workload’s scale subresource. The formula is one line: desiredReplicas = ceil(currentReplicas * currentMetricValue / desiredMetricValue). ...