Every organization needs to identify its services. But which approach is right? This guide compares the four most common machine identity strategies and explains when each excels.
SPIFFE/SPIRE
Best for: Cross-platform workload identity, multi-cloud, service mesh integration, Kubernetes-native identity.
- Automatic identity issuance via attestation
- Short-lived certificates with zero manual rotation
- Works across Kubernetes, VMs, bare metal, and cloud providers
- CNCF graduated standard — vendor-neutral
HashiCorp Vault PKI
Best for: Secret management combined with certificate issuance, organizations already using Vault.
- Strong secret storage and certificate management
- Rich policy system for secret access
- Requires Vault token distribution (creates its own secret management problem)
- Not a workload identity system — does not attest workloads
Kubernetes Service Accounts
Best for: Simple single-cluster Kubernetes deployments.
- Built into Kubernetes — no extra infrastructure
- Limited to one cluster — no federation
- Not cryptographic certificates — cannot be used for mTLS
- Tokens were long-lived before Kubernetes 1.24
Cloud IAM (AWS IAM, GCP Workload Identity)
Best for: Single-cloud deployments using cloud-native services.
- Deep integration with cloud provider services
- No infrastructure to manage
- Locked to one cloud provider — breaks in multi-cloud
- Not designed for service-to-service mTLS
Comparison Table
| Feature | SPIFFE/SPIRE | Vault PKI | K8s Service Accounts | Cloud IAM |
|---|---|---|---|---|
| Workload attestation | Yes | No | Limited | Cloud-specific |
| mTLS certificates | Yes (X.509-SVID) | Yes | No | No |
| Automatic rotation | Yes | Yes (with agent) | Partial (1.24+) | Yes |
| Multi-cloud | Yes | Yes | No | No |
| Federation | Yes (native) | Manual | No | Cross-account only |
| VM + Kubernetes | Yes | Yes | No | Partial |
| Open standard | CNCF (SPIFFE) | Proprietary | K8s-native | Proprietary |
The Right Choice Depends on Your Needs
Use SPIFFE/SPIRE when you need cross-platform, multi-cloud, or multi-cluster workload identity. Use Vault when secret management is the primary concern. Use K8s Service Accounts for simple single-cluster deployments. Use Cloud IAM for cloud-native services within a single provider.
For most organizations adopting zero trust, SPIFFE/SPIRE provides the most comprehensive and portable solution. Our free course teaches it from the ground up.