Machine Learning · head to head
Seldon vs Unleash
Seldon
Machine Learning
Kubernetes model serving whose current version is licensed under the Business Source Licence
- From
- Free
- Rated
- -
Unleash
Software Development
Open-source feature flag and experimentation service
- From
- Free
- Rated
- -
The short version
- Each has a real cost: Seldon seldon Core v2 is under the Business Source Licence rather than Apache 2.0, so production use requires a commercial agreement, and a team that evaluated it believing it was open source discovers the licence is the blocker exactly when the project is ready to ship.; Unleash the Pay-As-You-Go plan is priced per seat, which can get costly for larger teams.
- They diverge on capability: Seldon covers Kubernetes custom resources, Unleash covers Feature flags.
- Prices and features above were last checked on 30 August 2026.
Where they differ
Only the attributes on which Seldon and Unleash actually diverge.
Identical on both: starting price (Free), pricing model (freemium), free tier (Yes), user rating (Not yet rated).
What each one covers
Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.
Only in Seldon
- Kubernetes custom resources
- Inference graphs
- Traffic strategies
- Open Inference Protocol
- Alibi Explain
- Alibi Detect
- Kafka-backed pipelines in v2
- Commercial control plane
Only in Unleash
- Feature flags
- A/B/n testing
- Custom targeting
- SDKs
- SSO
- Audit logs
What people use each for
The jobs each tool is most often brought in to do.
Seldon
- Serving an ensemble or a multi-stage inference path as one versioned deployment rather than as a chain of separate servicesnot Unleash
- Running genuine production experiments where a share of live traffic goes to a candidate model and the results are comparednot Unleash
- Regulated environments needing explanations and drift monitoring attached to the served model rather than bolted on laternot Unleash
- Organisations with an established Kubernetes platform team who want serving expressed as manifests under existing deployment controlsnot Unleash
Unleash
- Gradual and progressive feature rolloutsnot Seldon
- Running A/B/n experiments tied to flagsnot Seldon
- Self-hosting feature management for compliance needsnot Seldon
- Enterprise SSO-controlled feature flag governancenot Seldon
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Seldon
- Seldon Core v2 is under the Business Source Licence rather than Apache 2.0, so production use requires a commercial agreement, and a team that evaluated it believing it was open source discovers the licence is the blocker exactly when the project is ready to ship.
- Core v1 remains Apache 2.0 but is in maintenance, so taking the free route means running software that receives no new development while the architecture it belongs to moves on without it.
- Version 2 is a different system rather than a newer release, with different custom resources, a scheduler component and a Kafka-based pipeline model, so migrating from v1 is a re-implementation of every deployment manifest rather than an upgrade.
- Kafka is a dependency for v2 pipelines, so an organisation that does not already operate it takes on a distributed log with its own storage, retention, rebalancing and failure modes purely in order to serve models.
- Everything assumes Kubernetes fluency and the failure modes are Kubernetes failure modes, custom resource version mismatches, an operator that will not reconcile, admission webhooks and resource limits terminating an inference pod mid-request, so it needs a platform engineer rather than a data scientist.
Unleash
- The Pay-As-You-Go plan is priced per seat, which can get costly for larger teams.
- Self-hosted Enterprise requires a minimum of 5 seats and an annual contract.
- Additional API traffic beyond the included quota is billed per million requests.
- Advanced SLAs and dedicated customer success are reserved for the custom Enterprise tier.
Pricing, plan by plan
Seldon
Free- Seldon CoreFree
- Open source
- Kubernetes deployment
- Model serving
- Seldon DeployFree
- Enterprise features
- GUI
- Monitoring
Unleash
Free- Pay-As-You-Go$75/month
- Cloud-hosted
- 53M API requests/month included
- Unlimited feature flags, projects and environments
- Custom Enterprise$undefined/mo
- Cloud, self-hosted or hybrid
- Premium support options
- 99.99% uptime SLA
Which should you pick?
Choose Seldon if
- You need kubernetes custom resources.
- You want to start without paying.
- You work on Linux.
- You also want inference graphs.
Choose Unleash if
- You need feature flags.
- You want to start without paying.
- You work on web, api, linux.
- You also want a/b/n testing.
Questions people ask
- Is Seldon or Unleash better?
- Neither clearly leads. Seldon starts at Free and Unleash at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Seldon or Unleash?
- Seldon starts at Free and Unleash at Free.
- Does Seldon or Unleash run on more platforms?
- Seldon runs on Linux. Unleash runs on web, api, linux.
- Can I use Seldon for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Seldon best used for?
- Seldon is most often used for serving an ensemble or a multi-stage inference path as one versioned deployment rather than as a chain of separate services, running genuine production experiments where a share of live traffic goes to a candidate model and the results are compared, regulated environments needing explanations and drift monitoring attached to the served model rather than bolted on later, organisations with an established kubernetes platform team who want serving expressed as manifests under existing deployment controls. Of those, serving an ensemble or a multi-stage inference path as one versioned deployment rather than as a chain of separate services and running genuine production experiments where a share of live traffic goes to a candidate model and the results are compared are not what Unleash is typically brought in for.
- What can Seldon do that Unleash cannot?
- Seldon covers Kubernetes custom resources, Inference graphs, Traffic strategies, Open Inference Protocol. Unleash covers Feature flags, A/B/n testing, Custom targeting, SDKs.
Answered from the vendors’ own pages
Seldon: Is Seldon open source?
Partly, and this is the thing to check before you build on it. Core v1 is Apache 2.0 but in maintenance. Core v2 was moved to the Business Source Licence in 2024, which allows evaluation but not unlicensed production use. Verify the current licence of each component you intend to run, including MLServer and the Alibi libraries.
Unleash: What does Unleash cost?
Unleash offers a Pay-As-You-Go cloud plan at $75/seat/month with a 14-day free trial, plus a custom-priced Enterprise plan for self-hosted or hybrid deployments.
SourceSeldon: What is the difference between v1 and v2?
Architecture, not just version number. v2 introduces a scheduler, a different set of custom resources and Kafka-backed pipelines. Manifests, mental model and operations all change, so treat a move as a project.
Unleash: How is usage metered?
The Pay-As-You-Go plan includes 53M API requests per month, with additional traffic billed at $5 per million requests thereafter.
SourceSeldon: Do I need Kubernetes?
Yes. It is a Kubernetes-native system and there is no meaningful deployment without a cluster and someone competent to run it.
Unleash: What does Unleash integrate with, and is there an API?
Unleash provides an API and 25+ official SDKs across languages, along with SSO integrations via SAML 2.0 and OpenID Connect.
SourceSeldon: What is MLServer?
Seldon's Python inference server implementing the Open Inference Protocol, usable inside Seldon deployments or on its own. Check its current licence alongside Core's, since the company has moved projects onto the Business Source Licence.
Seldon: Do I have to run Kafka?
For v2 pipelines, yes. If you only need single models served, that dependency is a large amount of infrastructure for the benefit, and a simpler serving layer may be the better answer.
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