Essentiële DevOps Interviewvragen: Complete Gids 2026

Bereid je voor op DevOps-interviews met onmisbare vragen over CI/CD, Kubernetes, Docker, Terraform en SRE-praktijken. Gedetailleerde antwoorden inbegrepen.

Essentiële DevOps Interviewvragen

DevOps-interviews toetsen een unieke combinatie van ontwikkelings-, operations- en automatiseringsvaardigheden. Deze gids bundelt de meest gestelde vragen, geordend per domein, met gestructureerde antwoorden die diepgaande beheersing van de concepten aantonen.

Voorbereidingstip

Naast technische kennis beoordeelt een recruiter het vermogen om complexe concepten eenvoudig uit te leggen en concrete probleemoplossende ervaringen te delen.

DevOps Fundamenten en Cultuur

Beginvragen peilen doorgaans naar het algehele begrip van de DevOps-filosofie.

V1: Wat is DevOps en welke problemen lost deze aanpak op?

DevOps vertegenwoordigt een cultuur en een set praktijken die softwareontwikkeling (Dev) en IT-operations (Ops) samenvoegen. Deze aanpak beoogt de ontwikkelcyclus te verkorten met behoud van hoge kwaliteit.

yaml
# devops-principles.yaml
# The pillars of DevOps culture
principles:
  collaboration:
    description: "Breaking silos between teams"
    practices:
      - "Shared responsibility for production code"
      - "Continuous communication via ChatOps"
      - "Blameless post-mortems"

  automation:
    description: "Automate repetitive tasks"
    practices:
      - "Infrastructure as Code (IaC)"
      - "CI/CD pipelines"
      - "Automated testing at all levels"

  measurement:
    description: "Measure to improve"
    metrics:
      - "Deployment frequency"
      - "Lead time for changes"
      - "Mean time to recovery (MTTR)"
      - "Change failure rate"

  sharing:
    description: "Share knowledge"
    practices:
      - "Documentation as Code"
      - "Automated runbooks"
      - "Regular knowledge sharing sessions"

Opgeloste problemen zijn onder meer trage en risicovolle deployments, gebrek aan zichtbaarheid tussen teams en inconsistentie over omgevingen heen.

V2: Wat is het verschil tussen CI, CD (Continuous Delivery) en CD (Continuous Deployment)?

Deze drie concepten vormen een progressie in de automatisering van de leveringscyclus.

bash
# ci-cd-pipeline-stages.sh
# Illustration of CI/CD stages

# ============================================
# CI (Continuous Integration)
# ============================================
# Goal: Frequently integrate code into a shared repository
# Automation: Build + Tests
echo "CI: Code commit → Build → Unit Tests → Integration Tests"

# ============================================
# CD (Continuous Delivery)
# ============================================
# Goal: Code always deployable to production
# Automation: CI + Staging deployment + Manual approval
echo "CD Delivery: CI → Deploy Staging → Manual Approval → Deploy Prod"

# ============================================
# CD (Continuous Deployment)
# ============================================
# Goal: Automatic deployment to production
# Automation: Entire pipeline without human intervention
echo "CD Deployment: CI → Deploy Staging → Auto Tests → Auto Deploy Prod"

Het kernverschil ligt in het niveau van automatisering: Continuous Delivery vereist handmatige validatie vóór productie, terwijl Continuous Deployment het volledige proces automatiseert.

CI/CD en Pipelines

CI/CD-vragen testen het vermogen om delivery pipelines te ontwerpen en te optimaliseren.

V3: Hoe structureer je een robuuste CI/CD-pipeline?

Een goed ontworpen pipeline volgt progressieve fasen met controlepunten op elk niveau.

yaml
# .gitlab-ci.yml
# Complete CI/CD pipeline with parallel and sequential stages
stages:
  - validate
  - build
  - test
  - security
  - deploy-staging
  - integration-tests
  - deploy-production

variables:
  DOCKER_IMAGE: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

# ============================================
# Stage 1: Fast validation (< 2 min)
# ============================================
lint:
  stage: validate
  script:
    - npm run lint
    - npm run type-check
  # Run on every commit
  rules:
    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
    - if: $CI_COMMIT_BRANCH

# ============================================
# Stage 2: Application build
# ============================================
build:
  stage: build
  script:
    - docker build -t $DOCKER_IMAGE .
    - docker push $DOCKER_IMAGE
  # Cache Docker layers to speed up builds
  cache:
    key: docker-$CI_COMMIT_REF_SLUG
    paths:
      - .docker-cache/

# ============================================
# Stage 3: Parallel tests
# ============================================
unit-tests:
  stage: test
  script:
    - npm run test:unit -- --coverage
  coverage: '/Lines\s*:\s*(\d+\.?\d*)%/'
  artifacts:
    reports:
      coverage_report:
        coverage_format: cobertura
        path: coverage/cobertura-coverage.xml

integration-tests:
  stage: test
  services:
    - postgres:16-alpine
    - redis:7-alpine
  script:
    - npm run test:integration
  # Parallelization with unit tests
  parallel: 3

# ============================================
# Stage 4: Security analysis
# ============================================
sast:
  stage: security
  script:
    - trivy image --exit-code 1 --severity HIGH,CRITICAL $DOCKER_IMAGE
  allow_failure: false

dependency-scan:
  stage: security
  script:
    - npm audit --audit-level=high
  allow_failure: true  # Alert without blocking

# ============================================
# Stage 5: Staging deployment
# ============================================
deploy-staging:
  stage: deploy-staging
  script:
    - kubectl set image deployment/app app=$DOCKER_IMAGE -n staging
    - kubectl rollout status deployment/app -n staging --timeout=300s
  environment:
    name: staging
    url: https://staging.example.com
  only:
    - develop

# ============================================
# Stage 6: E2E tests on staging
# ============================================
e2e-tests:
  stage: integration-tests
  script:
    - npm run test:e2e -- --base-url=https://staging.example.com
  artifacts:
    when: on_failure
    paths:
      - cypress/screenshots/
      - cypress/videos/
  only:
    - develop

# ============================================
# Stage 7: Production deployment
# ============================================
deploy-production:
  stage: deploy-production
  script:
    - kubectl set image deployment/app app=$DOCKER_IMAGE -n production
    - kubectl rollout status deployment/app -n production --timeout=300s
  environment:
    name: production
    url: https://app.example.com
  # Manual deployment with protection
  when: manual
  only:
    - main

Deze pipeline illustreert best practices: parallelle fasen voor snelheid, artefacten voor traceerbaarheid en beveiligde omgevingen voor productie.

V4: Hoe beheer je secrets in een CI/CD-pipeline?

Secretsbeheer vereist een meerlaagse aanpak die encryptie, rotatie en het principe van minimale privileges combineert.

yaml
# kubernetes-secrets-management.yaml
# Approach 1: External Secrets Operator with HashiCorp Vault
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: app-secrets
  namespace: production
spec:
  refreshInterval: 1h  # Automatic rotation
  secretStoreRef:
    name: vault-backend
    kind: ClusterSecretStore
  target:
    name: app-secrets
    creationPolicy: Owner
  data:
    # Reference to secret in Vault
    - secretKey: DATABASE_PASSWORD
      remoteRef:
        key: secret/data/production/database
        property: password
    - secretKey: API_KEY
      remoteRef:
        key: secret/data/production/api
        property: key
---
# SecretStore configuration
apiVersion: external-secrets.io/v1beta1
kind: ClusterSecretStore
metadata:
  name: vault-backend
spec:
  provider:
    vault:
      server: "https://vault.example.com"
      path: "secret"
      version: "v2"
      auth:
        kubernetes:
          mountPath: "kubernetes"
          role: "external-secrets"
          # Dedicated ServiceAccount with minimal permissions
          serviceAccountRef:
            name: external-secrets-sa

Aanbevolen praktijken: sla secrets nooit als platte tekst op in code, gebruik dedicated secret managers (Vault, AWS Secrets Manager) en schakel automatische rotatie in.

Anti-patroon

Vermijd CI/CD-omgevingsvariabelen die zichtbaar zijn in logs. Maskeer secrets altijd via de native functies van het CI-platform (masked variables).

Kubernetes en Orchestratie

Kubernetes-vragen beoordelen het begrip van orchestratieconcepten en het vermogen om concrete problemen op te lossen.

V5: Leg de Kubernetes-architectuur uit en de rol van elke component.

Kubernetes volgt een master-node-architectuur waarbij componenten duidelijk afgebakende verantwoordelijkheden hebben.

yaml
# kubernetes-architecture.yaml
# Control Plane components (Master)
control_plane:
  api_server:
    role: "Entry point for all API requests"
    responsibilities:
      - "Validation and configuration of API objects"
      - "Authentication and authorization"
      - "REST interface for kubectl and other clients"

  etcd:
    role: "Distributed key-value database"
    responsibilities:
      - "Cluster state storage"
      - "Source of truth for configuration"
      - "Consensus via Raft algorithm"

  scheduler:
    role: "Assigning Pods to nodes"
    responsibilities:
      - "Evaluating constraints (resources, affinity)"
      - "Selecting the optimal node"
      - "Respecting PodDisruptionBudgets"

  controller_manager:
    role: "Control loops for desired state"
    controllers:
      - "ReplicaSet Controller"
      - "Deployment Controller"
      - "Service Controller"
      - "Node Controller"

# Worker Node components
worker_nodes:
  kubelet:
    role: "Agent on each node"
    responsibilities:
      - "Communication with Control Plane"
      - "Pod lifecycle management"
      - "Node status reporting"

  kube_proxy:
    role: "Network proxy on each node"
    responsibilities:
      - "iptables/IPVS rules for Services"
      - "Intra-cluster load balancing"

  container_runtime:
    role: "Container execution"
    options:
      - "containerd (recommended)"
      - "CRI-O"

Deze architectuur maakt hoge beschikbaarheid mogelijk: het Control Plane kan worden gerepliceerd en workloads worden verdeeld over Worker Nodes.

V6: Hoe debug je een Pod die niet opstart?

Het debuggen van Kubernetes volgt een methodische aanpak waarbij verschillende lagen worden geanalyseerd.

bash
# kubernetes-debugging.sh
# Workflow for debugging a failing Pod

# Step 1: Check Pod status
kubectl get pod my-app-pod -o wide
# STATUS: CrashLoopBackOff, ImagePullBackOff, Pending, etc.

# Step 2: Pod details and events
kubectl describe pod my-app-pod
# Important sections:
# - Conditions (PodScheduled, Initialized, Ready)
# - Events (scheduling, pull errors, etc.)

# Step 3: Container logs
kubectl logs my-app-pod --previous  # Previous crash logs
kubectl logs my-app-pod -c init-container  # Init container logs

# Step 4: Interactive execution for debugging
kubectl exec -it my-app-pod -- sh
# Check: env vars, mounted files, network

# Step 5: Check available resources
kubectl describe node <node-name>
# Sections: Allocatable, Allocated resources

# Step 6: Debug with ephemeral Pod (K8s 1.25+)
kubectl debug my-app-pod -it --image=busybox --share-processes

Veelvoorkomende oorzaken zijn: onvoldoende resources, image niet gevonden, ontbrekende secrets of verkeerd geconfigureerde probes.

yaml
# pod-debugging-checklist.yaml
# Debugging checklist by status
debugging_by_status:
  Pending:
    causes:
      - "Insufficient resources on nodes"
      - "PersistentVolumeClaim not bound"
      - "Affinity/Taints not satisfied"
    commands:
      - "kubectl describe pod <name> | grep -A 20 Events"
      - "kubectl get pvc"
      - "kubectl describe nodes | grep -A 5 Allocated"

  ImagePullBackOff:
    causes:
      - "Non-existent image or incorrect tag"
      - "Private registry without imagePullSecrets"
      - "Docker Hub rate limiting"
    commands:
      - "kubectl get events --field-selector reason=Failed"
      - "kubectl get secret <pull-secret> -o yaml"

  CrashLoopBackOff:
    causes:
      - "Application error at startup"
      - "Missing configuration (env vars, configmaps)"
      - "Liveness probe too aggressive"
    commands:
      - "kubectl logs <pod> --previous"
      - "kubectl describe pod <pod> | grep -A 10 Liveness"

  OOMKilled:
    causes:
      - "Memory limit too low"
      - "Memory leak in application"
    commands:
      - "kubectl describe pod <pod> | grep -A 5 Last State"
      - "kubectl top pod <pod>"

Klaar om je DevOps gesprekken te halen?

Oefen met onze interactieve simulatoren, flashcards en technische tests.

Infrastructure as Code

IaC-vragen beoordelen de beheersing van provisioningtools en best practices.

V7: Terraform vs Ansible: wanneer gebruik je welk tool?

Deze tools hebben een duidelijk verschillende filosofie en toepassingsgebied.

hcl
# terraform-example.tf
# Terraform: Infrastructure provisioning (declarative)
# Ideal for: cloud resources, networking, infrastructure state

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
  # Remote state for collaboration
  backend "s3" {
    bucket         = "terraform-state-prod"
    key            = "infrastructure/terraform.tfstate"
    region         = "eu-west-1"
    dynamodb_table = "terraform-locks"
    encrypt        = true
  }
}

# Declarative resource: Terraform manages the lifecycle
resource "aws_eks_cluster" "main" {
  name     = "production-cluster"
  role_arn = aws_iam_role.eks_cluster.arn
  version  = "1.29"

  vpc_config {
    subnet_ids              = module.vpc.private_subnets
    endpoint_private_access = true
    endpoint_public_access  = false
  }

  # Implicit dependencies managed by Terraform
  depends_on = [
    aws_iam_role_policy_attachment.eks_cluster_policy
  ]
}

# Reusable modules for standardization
module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.0.0"

  name = "production-vpc"
  cidr = "10.0.0.0/16"

  azs             = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  public_subnets  = ["10.0.101.0/24", "10.0.102.0/24", "10.0.103.0/24"]

  enable_nat_gateway = true
  single_nat_gateway = false  # HA: one NAT per AZ
}
yaml
# ansible-example.yml
# Ansible: Configuration management (procedural/declarative)
# Ideal for: OS configuration, app deployment, orchestration

---
- name: Configure application servers
  hosts: app_servers
  become: yes
  vars:
    app_version: "2.5.0"

  tasks:
    # System package management
    - name: Install required packages
      ansible.builtin.apt:
        name:
          - nginx
          - python3-pip
          - supervisor
        state: present
        update_cache: yes

    # Configuration via Jinja2 templates
    - name: Deploy nginx configuration
      ansible.builtin.template:
        src: templates/nginx.conf.j2
        dest: /etc/nginx/sites-available/app
        owner: root
        group: root
        mode: '0644'
      notify: Reload nginx

    # Application deployment
    - name: Deploy application
      ansible.builtin.git:
        repo: "https://github.com/org/app.git"
        dest: /opt/app
        version: "v{{ app_version }}"
      notify: Restart application

  handlers:
    - name: Reload nginx
      ansible.builtin.service:
        name: nginx
        state: reloaded

    - name: Restart application
      ansible.builtin.supervisorctl:
        name: app
        state: restarted

Samengevat: Terraform voor infrastructuur (wat er bestaat), Ansible voor configuratie (hoe het geconfigureerd is). Beide tools worden vaak gecombineerd in een volledig workflow.

V8: Hoe structureer je een Terraform-project voor een grote organisatie?

Een modulaire structuur met omgevingsscheiding vergemakkelijkt onderhoud en samenwerking.

bash
# terraform-project-structure
# Recommended structure for enterprise projects

terraform-infrastructure/
├── modules/                    # Reusable modules
│   ├── networking/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   ├── outputs.tf
│   │   └── README.md
│   ├── kubernetes/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   └── database/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
├── environments/               # Per-environment configuration
│   ├── dev/
│   │   ├── main.tf            # Calls modules
│   │   ├── variables.tf
│   │   ├── terraform.tfvars   # Dev values
│   │   └── backend.tf         # Dev state
│   ├── staging/
│   │   ├── main.tf
│   │   ├── terraform.tfvars
│   │   └── backend.tf
│   └── production/
│       ├── main.tf
│       ├── terraform.tfvars
│       └── backend.tf
├── shared/                     # Shared resources
│   ├── iam/
│   └── dns/
└── .github/
    └── workflows/
        └── terraform.yml      # CI/CD pipeline
hcl
# environments/production/main.tf
# Example of module usage

module "networking" {
  source = "../../modules/networking"

  environment     = "production"
  vpc_cidr        = var.vpc_cidr
  azs             = var.availability_zones
  enable_flow_logs = true
}

module "kubernetes" {
  source = "../../modules/kubernetes"

  environment    = "production"
  cluster_name   = "prod-cluster"
  vpc_id         = module.networking.vpc_id
  subnet_ids     = module.networking.private_subnet_ids
  node_groups    = var.node_groups

  # Production: HA configuration
  cluster_version           = "1.29"
  enable_cluster_autoscaler = true
}

module "database" {
  source = "../../modules/database"

  environment        = "production"
  vpc_id             = module.networking.vpc_id
  subnet_ids         = module.networking.database_subnet_ids
  instance_class     = "db.r6g.xlarge"
  multi_az           = true  # HA in production
  backup_retention   = 30
}

Deze structuur maakt mogelijk: moduleversioning, wijzigingsbeoordeling per omgeving en hergebruik van code.

Monitoring en Observability

Monitoringvragen beoordelen het vermogen om observeerbare systemen te ontwerpen.

V9: Wat zijn de drie pijlers van observability?

Observability steunt op drie complementaire datatypes die helpen de interne toestand van een systeem te begrijpen.

yaml
# observability-pillars.yaml
# The three pillars of observability

pillars:
  metrics:
    description: "Numeric data aggregated over time"
    characteristics:
      - "Low cardinality"
      - "Efficient storage"
      - "Ideal for alerting"
    examples:
      - "request_count (counter)"
      - "response_time_seconds (histogram)"
      - "active_connections (gauge)"
    tools:
      - "Prometheus"
      - "Datadog"
      - "CloudWatch"
    use_cases:
      - "Real-time dashboards"
      - "Threshold alerts"
      - "Capacity planning"

  logs:
    description: "Timestamped text events"
    characteristics:
      - "High cardinality"
      - "Detailed context"
      - "Large storage"
    examples:
      - "Application errors"
      - "Audit events"
      - "Debug information"
    tools:
      - "Loki"
      - "Elasticsearch"
      - "CloudWatch Logs"
    use_cases:
      - "Debugging"
      - "Audit compliance"
      - "Root cause analysis"

  traces:
    description: "Request tracking across services"
    characteristics:
      - "End-to-end view"
      - "Context propagation"
      - "Bottleneck identification"
    examples:
      - "Distributed transaction"
      - "Service dependencies"
      - "Latency breakdown"
    tools:
      - "Jaeger"
      - "Tempo"
      - "AWS X-Ray"
    use_cases:
      - "Performance optimization"
      - "Service dependencies"
      - "Error propagation"

V10: Hoe configureer je effectieve alerts?

Goed ontworpen alerts verminderen moeheid en maken snelle incidentrespons mogelijk.

yaml
# prometheus-alerting-rules.yaml
# Prometheus alerting rules with best practices

groups:
  - name: application-alerts
    rules:
      # Alert on symptom, not cause
      - alert: HighErrorRate
        # Error rate > 1% over 5 minutes
        expr: |
          sum(rate(http_requests_total{status=~"5.."}[5m]))
          /
          sum(rate(http_requests_total[5m]))
          > 0.01
        for: 5m  # Avoid false positives
        labels:
          severity: critical
          team: backend
        annotations:
          summary: "High error rate detected"
          description: |
            Error rate is {{ $value | humanizePercentage }}
            for the last 5 minutes.
          runbook_url: "https://wiki.example.com/runbooks/high-error-rate"

      # Proactive alert on saturation
      - alert: DiskSpaceRunningLow
        expr: |
          (node_filesystem_avail_bytes / node_filesystem_size_bytes)
          * 100 < 20
        for: 15m
        labels:
          severity: warning
        annotations:
          summary: "Disk space below 20%"
          description: |
            Node {{ $labels.instance }} has only
            {{ $value | humanize }}% disk space remaining.

      # SLO-based alerting
      - alert: SLOBudgetBurnRate
        # Error budget consumed too quickly
        expr: |
          (
            sum(rate(http_requests_total{status=~"5.."}[1h]))
            /
            sum(rate(http_requests_total[1h]))
          ) > (1 - 0.999) * 14.4
        for: 5m
        labels:
          severity: critical
        annotations:
          summary: "SLO budget burning too fast"
          description: |
            At current error rate, monthly SLO budget will be
            exhausted in less than 2 days.
yaml
# alertmanager-config.yaml
# AlertManager configuration with intelligent routing

global:
  resolve_timeout: 5m

route:
  receiver: default
  group_by: [alertname, cluster, service]
  group_wait: 30s       # Wait to group alerts
  group_interval: 5m    # Interval between grouped notifications
  repeat_interval: 4h   # Re-alert if not resolved

  routes:
    # Critical alerts: immediate notification
    - match:
        severity: critical
      receiver: pagerduty-critical
      continue: true  # Also notify Slack

    # Alerts by team
    - match:
        team: backend
      receiver: slack-backend

    - match:
        team: infrastructure
      receiver: slack-infra

receivers:
  - name: pagerduty-critical
    pagerduty_configs:
      - service_key: <pagerduty-key>
        severity: critical

  - name: slack-backend
    slack_configs:
      - channel: '#alerts-backend'
        send_resolved: true
        title: '{{ .Status | toUpper }}: {{ .CommonAnnotations.summary }}'
        text: '{{ .CommonAnnotations.description }}'

Kernprincipes: alert op symptomen (gebruikersimpact) in plaats van oorzaken, voeg runbooks toe en stem drempelwaarden af op SLO's.

Beveiliging en Compliance

Beveiligingsvragen beoordelen het begrip van risico's en tegenmaatregelen.

V11: Hoe beveilig je een Kubernetes-cluster?

Kubernetes-beveiliging omvat meerdere lagen: netwerk, authenticatie, workloads en data.

yaml
# kubernetes-security-policies.yaml
# NetworkPolicy: network isolation between namespaces

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: production
spec:
  # Applied to all pods in namespace
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress
  # No traffic allowed by default
  ingress: []
  egress: []
---
# Allow only necessary traffic
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: api-network-policy
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: api
  policyTypes:
    - Ingress
    - Egress
  ingress:
    # Accept only from ingress controller
    - from:
        - namespaceSelector:
            matchLabels:
              name: ingress-nginx
      ports:
        - protocol: TCP
          port: 8080
  egress:
    # Allow to database
    - to:
        - podSelector:
            matchLabels:
              app: postgres
      ports:
        - protocol: TCP
          port: 5432
    # Allow DNS
    - to:
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - protocol: UDP
          port: 53
yaml
# pod-security-standards.yaml
# PodSecurity: workload restrictions

apiVersion: v1
kind: Namespace
metadata:
  name: production
  labels:
    # Enforce: blocks violations
    pod-security.kubernetes.io/enforce: restricted
    # Warn: warns without blocking
    pod-security.kubernetes.io/warn: restricted
    # Audit: logs violations
    pod-security.kubernetes.io/audit: restricted
---
# Pod compliant with "restricted" standards
apiVersion: v1
kind: Pod
metadata:
  name: secure-pod
  namespace: production
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 1000
    seccompProfile:
      type: RuntimeDefault
  containers:
    - name: app
      image: myapp:latest
      securityContext:
        allowPrivilegeEscalation: false
        readOnlyRootFilesystem: true
        capabilities:
          drop:
            - ALL
      resources:
        limits:
          memory: "256Mi"
          cpu: "500m"
        requests:
          memory: "128Mi"
          cpu: "250m"
      volumeMounts:
        - name: tmp
          mountPath: /tmp
  volumes:
    - name: tmp
      emptyDir: {}
Defense in depth

Kubernetes-beveiliging combineert meerdere lagen: RBAC voor autorisatie, NetworkPolicies voor netwerkirsolatie, PodSecurity voor workloadbeperkingen en versleuteling van secrets in rust.

V12: Wat is het principe van minimale privileges en hoe pas je het toe?

Dit principe stelt dat een gebruiker of systeem alleen de minimale permissies mag hebben die nodig zijn om de taak uit te voeren.

yaml
# rbac-least-privilege.yaml
# Kubernetes RBAC with minimal permissions

# Role: permissions in a specific namespace
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: production
  name: deployment-manager
rules:
  # Pod reading (for monitoring)
  - apiGroups: [""]
    resources: ["pods", "pods/log"]
    verbs: ["get", "list", "watch"]
  # Deployment management only
  - apiGroups: ["apps"]
    resources: ["deployments"]
    verbs: ["get", "list", "watch", "update", "patch"]
  # No create/delete on deployments
  # No access to secrets or sensitive configmaps
---
# RoleBinding: Role <-> ServiceAccount association
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: deployment-manager-binding
  namespace: production
subjects:
  - kind: ServiceAccount
    name: ci-cd-deployer
    namespace: production
roleRef:
  kind: Role
  name: deployment-manager
  apiGroup: rbac.authorization.k8s.io
---
# Dedicated ServiceAccount for CI/CD
apiVersion: v1
kind: ServiceAccount
metadata:
  name: ci-cd-deployer
  namespace: production
  annotations:
    # Automatic token expiration
    kubernetes.io/enforce-mountable-secrets: "true"

Dit principe geldt ook voor AWS IAM, databases en netwerktoegang.

SRE en Betrouwbaarheid

SRE-vragen beoordelen het begrip van betrouwbaarheidspraktijken en incidentbeheer.

V13: Wat is een SLO en hoe definieer je het?

Service Level Objectives (SLO's) kwantificeren de verwachte betrouwbaarheid van een service en sturen technische beslissingen.

yaml
# slo-definitions.yaml
# SLO definitions for an API service

service: payment-api
owner: payments-team

slos:
  - name: availability
    description: "Service responds successfully to requests"
    sli:
      # SLI: measured metric
      type: availability
      good_events: "http_requests_total{status=~'2..'}"
      total_events: "http_requests_total"
    target: 99.9%  # SLO: objective
    window: 30d    # Measurement window
    # Error budget: 0.1% = 43.2 minutes/month
    error_budget:
      monthly_minutes: 43.2

  - name: latency
    description: "Response time below threshold"
    sli:
      type: latency
      good_events: "http_request_duration_seconds_bucket{le='0.3'}"
      total_events: "http_request_duration_seconds_count"
    target: 99%  # 99% of requests < 300ms
    window: 30d

  - name: throughput
    description: "Ability to process transactions"
    sli:
      type: throughput
      query: "sum(rate(transactions_processed_total[5m]))"
    target: ">= 1000 TPS"

# Actions based on error budget
error_budget_policy:
  - condition: "remaining > 50%"
    actions:
      - "Feature development prioritized"
      - "Experimentation allowed"
  - condition: "remaining 20-50%"
    actions:
      - "Balance features and reliability"
      - "Increase testing coverage"
  - condition: "remaining < 20%"
    actions:
      - "Freeze non-critical deployments"
      - "Focus on reliability improvements"
  - condition: "exhausted"
    actions:
      - "Incident response mode"
      - "All hands on reliability"

SLO's maken objectieve beslissingen mogelijk: een nieuwe functie deployen versus betrouwbaarheid versterken.

V14: Hoe voer je een effectieve post-mortem uit?

Een blameless post-mortem bevordert leren en het voorkomen van toekomstige incidenten.

yaml
# postmortem-template.yaml
# Blameless post-mortem template

incident:
  id: "INC-2026-0042"
  title: "Payment service unavailability"
  severity: SEV1
  duration: "45 minutes"
  date: "2026-01-15"

# Factual timeline
timeline:
  - time: "14:32"
    event: "Alert: error rate > 5% on payment-api"
    actor: "PagerDuty"
  - time: "14:35"
    event: "Incident declared, team notified"
    actor: "On-call engineer"
  - time: "14:42"
    event: "Cause identified: connection pool exhausted"
    actor: "Backend team"
  - time: "14:55"
    event: "Mitigation: deployment rollback"
    actor: "Backend team"
  - time: "15:17"
    event: "Service restored, monitoring stable"
    actor: "Backend team"

# Measurable impact
impact:
  users_affected: 12500
  transactions_failed: 847
  revenue_impact: "~$16,500"
  slo_budget_consumed: "2.3 days"

# Root cause analysis (5 Whys)
root_cause_analysis:
  - question: "Why was the service unavailable?"
    answer: "DB connections were exhausted"
  - question: "Why were connections exhausted?"
    answer: "A slow query was blocking connections"
  - question: "Why was there a slow query?"
    answer: "Missing index on a new table"
  - question: "Why was the index missing?"
    answer: "Incomplete migration deployed"
  - question: "Why was the migration incomplete?"
    answer: "No execution plan validation in staging"

# Corrective actions
action_items:
  - id: "AI-001"
    type: "prevent"
    description: "Add SQL execution plan validation in CI"
    owner: "DBA team"
    due_date: "2026-01-22"
    priority: P1

  - id: "AI-002"
    type: "detect"
    description: "Alert on connection pool usage > 80%"
    owner: "SRE team"
    due_date: "2026-01-18"
    priority: P1

  - id: "AI-003"
    type: "mitigate"
    description: "Implement circuit breaker on DB queries"
    owner: "Backend team"
    due_date: "2026-01-29"
    priority: P2

# Lessons learned
lessons_learned:
  what_went_well:
    - "Fast detection thanks to alerting (< 3 min)"
    - "Clear communication in incident channel"
    - "Rollback completed in less than 15 minutes"
  what_went_poorly:
    - "No load testing on new endpoint"
    - "Staging didn't reflect prod data volume"
  lucky:
    - "Incident during daytime with full team available"

Het doel is het systeem verbeteren, niet een schuldige aanwijzen. Acties worden ingedeeld in drie categorieën: preventie, detectie en mitigatie.

Begin met oefenen!

Test je kennis met onze gespreksimulatoren en technische tests.

Conclusie

DevOps-interviews bestrijken een breed spectrum van vaardigheden, van cultuur tot technische tools. De sleutel tot succes ligt in het aantonen van diepgaand begrip van concepten, geïllustreerd door concrete implementatievoorbeelden.

Voorbereidingschecklist

  • ✅ Beheers CI/CD-concepten en wees in staat een complete pipeline te ontwerpen
  • ✅ Begrijp de Kubernetes-architectuur en wees in staat veelvoorkomende problemen te debuggen
  • ✅ Ken IaC-tools (Terraform, Ansible) en hun respectievelijke toepassingsgebieden
  • ✅ Weet hoe je monitoring configureert en relevante alerts definieert
  • ✅ Pas beveiligingsbest practices toe (minimale privileges, defense in depth)
  • ✅ Leg SRE-praktijken uit (SLO's, error budgets, post-mortems)
  • ✅ Beschik over concrete voorbeelden van probleemoplossing
  • ✅ Wees in staat complexe concepten eenvoudig uit te leggen

Tags

#devops
#interview
#ci cd
#kubernetes
#infrastructure

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