📘 Kubernetes Workload Types – A Simple Comparison Guide 📘
Choosing the right Kubernetes controller is key to successful application deployment. Here's a quick comparison to guide your decision-making.
| Type / Pattern | Purpose | Pod Identity | Scaling | Use Case | Example |
|---|---|---|---|---|---|
| Pod | Smallest deployable unit representing a single instance of a containerized app | Ephemeral | Not self-managed | Ad-hoc testing or one-off utility execution | Run a .NET CLI command to test a legacy service migration in isolation |
| ReplicaSet | Maintains a fixed number of pod replicas for high availability | Ephemeral | Automatic (based on replicas) | Ensures multiple instances of stateless services remain available | Ensure 3 instances of a .NET microservice for invoice processing are always running |
| Deployment | Manages rolling updates, scaling, and rollback for stateless applications | Ephemeral | Manual or via HPA | Ideal for microservices needing frequent updates and scalability | Deploy a .NET Core customer service with zero downtime during upgrades |
| StatefulSet | Supports stateful apps requiring stable identities and persistent storage | Stable | Manual or HPA | Best for microservices with ordered startup and volume claims | Host a .NET-based order tracking system that requires sticky sessions and persistence |
| DaemonSet | Ensures that a pod runs on all (or selected) nodes | Tied to nodes | One per node | Used for logging, monitoring, or security agents across cluster nodes | Deploy a .NET agent to collect metrics/logs from each node during app modernization |
| Job | Runs pods until a task completes successfully | Ephemeral | N/A | Perfect for migration scripts or backend processing tasks | Trigger a .NET Core migration script to convert monolith DB schemas |
| CronJob | Runs scheduled Jobs at specific time intervals | Ephemeral | N/A | Ideal for recurring batch processes in a modernized pipeline | Run a scheduled .NET Core job for nightly report generation or cleanup tasks |
| Sidecar | Runs with the main app container, extending its capabilities | Shared | With main container | Used for service mesh, configuration reloads, and observability | Use Dapr as a sidecar to a .NET microservice for state management or pub/sub integration |
| Init Container | Runs before the main app to prepare the environment | Runs once | N/A | Helps decouple setup logic from the main service logic | Run a .NET tool to apply Entity Framework DB migrations before a microservice starts |
| Service | Exposes a group of pods as a stable network endpoint | Fronts pods | N/A | Handles internal and external traffic routing | Expose a .NET monolith or microservice as a ClusterIP for internal APIs or LoadBalancer for public APIs |
| HPA | Scales pods horizontally based on real-time metrics | Depends on metrics | Dynamic | Optimizes performance for fluctuating workloads | Auto-scale a .NET product catalog microservice during peak user activity |
| VPA | Dynamically adjusts resource requests based on usage | Dynamic | N/A | Optimizes resource consumption for consistent workloads | Tune memory and CPU for a .NET payment processing service running consistently under load |
| Job Controller | Orchestrates execution and retries of multiple Jobs | Ephemeral | N/A | Enables batch job orchestration and error handling | Run and monitor multiple .NET batch jobs for ETL during migration from a legacy data warehouse |
Design Considerations Before Choosing a Workload
- Pod Identity: Do pods need a stable identity (like in StatefulSets) or are they interchangeable (like in Deployments)?
- State Persistence: Will the workload require persistent storage, or is it ephemeral in nature?
- Scalability: Will it need to scale automatically based on load or metrics?
- Startup Requirements: Does the application need any setup steps before starting the main container?
- Scheduling Pattern: Is the task a long-running service or a scheduled/one-time job?
- Node Affinity: Should the workload be deployed on every node (e.g., DaemonSets)?
- Resource Tuning: Is vertical or horizontal pod autoscaling required?
- Lifecycle Management: Do you need declarative updates and rollbacks (Deployments), or precise ordering (StatefulSets)?
Quick Recommendations
- Deployment: For most stateless, scalable applications
- StatefulSet: For databases or apps requiring persistence
- DaemonSet: For node-level operations/logging
- Job/CronJob: For one-off or scheduled batch tasks
- Sidecar: For shared functionality like proxying or observability
- Init Container: For setup or preparation logic