Autoscaling Controller  ·  View 04 of 37  ·  1 · Context and scope

Layered Architecture

Seven layers, and the one rule about which way they may call.

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Configuration and control Target Registry versioned Policy Catalogue immutable versions Bounds and Ceilings outside the policy Overrides expiry mandatory Signal plane Collectors authenticated sources Normaliser Derived Signals named expressions Freshness Gate Signal Store Mimir · 13 months Decision plane Policy Evaluation sharded Combination Rule max out, min in Stability Controls hysteresis, limits Oscillation Guard freeze and alert Desired-state record Desired Capacity per Target strongly consistent · the truth Actuation plane Reconciler no policy logic Provider Adapters Warm-Pool Manager Drain Coordinator Registration Check Managed capacity Service Groups VMSS Worker Pools queue driven Node Groups AKS Warm Pools attach in 10 s Observability Decision Journal append only Controller Metrics Alerts Cost Reporting Counterfactual Replay Layered Architecture Data store Security / platform Application we own Decision point Interface / broker External / third party A layer may call the layer below it and read the layer above it. Bounds live above the policy that would otherwise compute them. v 1.0 · owner Data & AI Global Practice · date 2026-09

Decisions

  • Bounds and ceilings sit in the configuration layer, above the decision plane, so no policy can breach a limit it also computes.
  • The desired-state record is its own layer rather than a component of either plane, because both planes depend on it and neither owns it.
  • Observability reads every layer and is read by none of them, so losing it degrades explanation and never control.

Reading rule

  • A layer may call the layer below it and read the layer above it.
  • The signal plane may not call the actuation plane. The actuation plane may not read the signal plane.

Assumptions

  • This is the only view in the set drawn as stacked bands. Every other view has the shape its own kind of question needs.
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Solution Architecture v1.0 · Data & AI Global Practice · 2026-09 · 37 views · Azure and open source04-layered-architecture