Chapter 08: Availability Engineering (HPA + PDB)

Why This Chapter Exists

Replicas alone do not guarantee availability during disruption. This chapter combines:

• HPA for load-based scaling
• PDB for controlled voluntary disruptions
• rollout/drain awareness

Guardrails

• staging/production start from 2 replicas for critical services.
• each service has HPA bounds (minReplicas, maxReplicas) and resource targets.
• each service has PDB to prevent unsafe disruption.
• node drain or rollout is never executed without checking PDB/HPA state.

Repo Mapping

Platform repository references:

• Backend overlays
• Frontend overlays
• Backend HPA/PDB (develop)
• Frontend HPA/PDB (develop)

Current Implementation (This Repo)

• HPA (autoscaling/v2) added for backend and frontend in all three environments.
• PDB (policy/v1) added for backend and frontend in all three environments.
• staging/production baseline replicas are 2 for backend and frontend.

Lab Files

• lab.md
• quiz.md

Done When

• learner can verify HPA target/bounds and current scaling state
• learner can verify PDB allowed disruptions before node drain
• learner can explain interaction: HPA, PDB, rollout, and drain