Kubernetes Architecture

Principles and patterns for designing production-ready Kubernetes environments.

When to Use

• Designing new Kubernetes deployments
• Planning cluster topology and network architecture
• Implementing multi-cluster strategies
• Evaluating Kubernetes distribution options
• Migrating workloads to Kubernetes

Cluster Architecture Patterns

Single Cluster / Multi-Environment

Single Kubernetes Cluster
├── Namespace: production
│   ├── Network Policy
│   ├── Resource Quotas
│   ├── RBAC: Production Team
│   └── Workloads with high QoS
├── Namespace: staging
│   ├── Network Policy
│   ├── Resource Quotas
│   ├── RBAC: Dev Teams
│   └── Workloads with medium QoS
└── Namespace: development
    ├── Network Policy
    ├── Resource Quotas
    ├── RBAC: Dev Teams
    └── Workloads with low QoS

Best for:

• Small to medium-sized teams
• Limited operational resources
• Starting Kubernetes journey
• Testing/development with moderate isolation needs

Environment-Based Clusters

Production Cluster          Staging Cluster           Development Cluster
├── Stringent Security      ├── Standard Security     ├── Relaxed Security
├── High Reliability        ├── Medium Reliability    ├── Basic Reliability
├── Production Workloads    ├── Pre-production Tests  ├── Development Work
├── Limited Access          ├── Team Access           └── Developer Access
└── Strict Change Control   └── Managed Changes

Best for:

• Strict isolation requirements
• Different security/compliance needs per environment
• Separate upgrade cycles
• Independent scalability requirements

Multi-Region / Multi-Cloud

Primary Region (AWS)         Secondary Region (Azure)
├── Production Cluster       ├── DR Cluster
│   ├── Active Workloads     │   ├── Passive/Active Workloads
│   ├── Primary Data         │   ├── Replicated Data
│   └── Full Traffic         │   └── Failover Traffic
├── Staging Cluster          └── Limited Staging
└── Development Cluster

Best for:

• High availability requirements
• Geographic distribution needs
• Regulatory/compliance requirements
• Disaster recovery objectives
• Cloud provider redundancy

Node Architecture Patterns

Dedicated Node Pools

Kubernetes Cluster
├── System Node Pool (Small VMs)
│   └── System Components (CoreDNS, Metrics, etc.)
├── General Purpose Pool (Medium VMs)
│   └── Stateless Applications
├── Memory-Optimized Pool (High Memory VMs)
│   └── In-Memory Databases, Caches
├── Compute-Optimized Pool (High CPU VMs)
│   └── Batch Processing, ML Workloads
└── Storage-Optimized Pool (High Disk I/O VMs)
    └── Databases, Storage Systems

Best for:

• Mixed workload characteristics
• Cost optimization
• Performance isolation
• Specialized hardware requirements

Node Placement Strategy

Kubernetes Workloads
├── Node Affinity/Anti-Affinity
│   └── Place workloads on specific nodes
├── Pod Affinity/Anti-Affinity
│   └── Control pod-to-pod placement
├── Taints and Tolerations
│   └── Restrict which pods run on nodes
└── Topology Spread Constraints
    └── Distribute pods across failure domains

Implementation:

# Node affinity example
affinity:
  nodeAffinity:
    requiredDuringSchedulingIgnoredDuringExecution:
      nodeSelectorTerms:
      - matchExpressions:
        - key: node-type
          operator: In
          values:
          - memory-optimized

Networking Models

Cluster Networking

Network Security Pattern

                      ┌─────────────────────────────────────┐
                      │ Network Policy: default-deny-all    │
                      └─────────────────────────────────────┘
                                       │
                                       ▼
┌─────────────────────┐      ┌─────────────────────┐      ┌─────────────────────┐
│ Namespace: frontend │      │ Namespace: backend  │      │ Namespace: database │
│ ┌─────────────────┐ │      │ ┌─────────────────┐ │      │ ┌─────────────────┐ │
│ │ Allow ingress   │◄┼──────┼─┤ Allow frontend  │ │      │ │ Allow backend   │ │
│ │ from Internet   │ │      │ │ namespace       │◄┼──────┼─┤ namespace       │ │
│ └─────────────────┘ │      │ └─────────────────┘ │      │ └─────────────────┘ │
│ ┌─────────────────┐ │      │ ┌─────────────────┐ │      │ ┌─────────────────┐ │
│ │ Allow egress to │ │      │ │ Allow egress to │ │      │ │ Deny all other  │ │
│ │ backend only    │─┼─────►│ │ database only   │─┼─────►│ │ traffic         │ │
│ └─────────────────┘ │      │ └─────────────────┘ │      │ └─────────────────┘ │
└─────────────────────┘      └─────────────────────┘      └─────────────────────┘

Control Plane Patterns

Highly Available Control Plane

┌───────────────────────────────────────────────────────────┐
│ Control Plane - Multi-AZ/Multi-Zone                       │
│ ┌─────────────┐  ┌─────────────┐  ┌─────────────┐         │
│ │ AZ 1        │  │ AZ 2        │  │ AZ 3        │         │
│ │ ┌─────────┐ │  │ ┌─────────┐ │  │ ┌─────────┐ │         │
│ │ │API Server│ │  │ │API Server│ │  │ │API Server│ │         │
│ │ └─────────┘ │  │ └─────────┘ │  │ └─────────┘ │         │
│ │ ┌─────────┐ │  │ ┌─────────┐ │  │ ┌─────────┐ │         │
│ │ │Controller│ │  │ │Controller│ │  │ │Controller│ │         │
│ │ │Manager   │ │  │ │Manager   │ │  │ │Manager   │ │         │
│ │ └─────────┘ │  │ └─────────┘ │  │ └─────────┘ │         │
│ │ ┌─────────┐ │  │ ┌─────────┐ │  │ ┌─────────┐ │         │
│ │ │Scheduler │ │  │ │Scheduler │ │  │ │Scheduler │ │         │
│ │ └─────────┘ │  │ └─────────┘ │  │ └─────────┘ │         │
│ └─────────────┘  └─────────────┘  └─────────────┘         │
└───────────────────────────────────────────────────────────┘
                          │
┌─────────────────────────▼───────────────────────────────────┐
│ Distributed etcd                                            │
│ ┌─────────┐            ┌─────────┐            ┌─────────┐   │
│ │ etcd 1  │◄──────────►│ etcd 2  │◄──────────►│ etcd 3  │   │
│ │ (AZ 1)  │            │ (AZ 2)  │            │ (AZ 3)  │   │
│ └─────────┘            └─────────┘            └─────────┘   │
└───────────────────────────────────────────────────────────────┘

Key recommendations:

• Control plane components in each AZ/Zone
• Odd number of etcd instances (3, 5, 7) across zones
• Node auto-repair and auto-upgrade
• Separate system workloads from user workloads
• Control plane scaling for large clusters (>100 nodes)

Storage Architecture

Storage Class Strategy

# Performance-optimized
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: performance
provisioner: kubernetes.io/aws-ebs
parameters:
  type: io1
  iopsPerGB: "50"
  fsType: ext4
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
---
# Cost-optimized
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: standard
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp3
  fsType: ext4
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true

Best practices:

• Use WaitForFirstConsumer binding mode
• Create purpose-specific storage classes
• Enable volume expansion
• Configure appropriate reclaim policies
• Implement backup solutions

Multi-Cluster Management

Federation Pattern

┌───────────────────────────────────┐
│ Management Cluster                │
│ ┌───────────────────────────────┐ │
│ │ Cluster API                   │ │
│ │ ┌─────────┐ ┌─────────┐      │ │
│ │ │Providers│ │Templates│      │ │
│ │ └─────────┘ └─────────┘      │ │
│ └───────────────────────────────┘ │
│ ┌───────────────────────────────┐ │
│ │ Fleet Management             │ │
│ │ ┌─────────┐ ┌─────────┐      │ │
│ │ │Config   │ │Workload │      │ │
│ │ │Sync     │ │Placement│      │ │
│ │ └─────────┘ └─────────┘      │ │
│ └───────────────────────────────┘ │
└───────────────────────────────────┘
            │         │         │
      ┌─────▼─┐  ┌────▼──┐  ┌───▼───┐
      │Cluster│  │Cluster│  │Cluster│
      │  1    │  │  2    │  │  3    │
      └───────┘  └───────┘  └───────┘

Implementation options:

• Cluster API for provisioning
• Fleet management (Config Sync, Karmada, KubeFed)
• Service mesh federation (Istio multi-cluster)
• GitOps for configuration management

Managed vs Self-Managed Decision Matrix

Production Readiness Checklist

• High availability control plane
• Node auto-scaling configuration
• Pod disruption budgets for critical services
• Resource requests/limits for all workloads
• Network policies defined for all namespaces
• Ingress with TLS configuration
• RBAC with least privilege
• Monitoring and alerting
• Logging and audit trail
• Backup and disaster recovery
• Upgrade strategy
• Security scanning and policy enforcement