Cloud · head to head
Fly.io vs Keycloak
Keycloak
Developer Tools
Open-source identity and access management server.
- From
- Free
- Free plan
- Yes
The short version
- Only Keycloak has a free tier, so it costs nothing to try first.
- Each has a real cost: Fly.io egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are; Keycloak requires self-hosted deployment and operational expertise to install, configure and maintain
- Prices and features above were last checked on 30 August 2026.
Where they differ
Only the attributes on which Fly.io and Keycloak actually diverge.
Identical on both: 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 Fly.io
- Global deployment
- Docker support
- Postgres databases
- Redis support
- Auto-scaling
- Health checks
- Backups
- Monitoring
Only in Keycloak
Nothing recorded that Fly.io does not also cover.
What people use each for
The jobs each tool is most often brought in to do.
Fly.io
- Deploying containerised applications close to users across regionsnot Keycloak
- Running full stack apps and databases on managed machinesnot Keycloak
Keycloak
- Organisations requiring self-hosted identity infrastructure for compliance or data residencynot Fly.io
- Companies with existing LDAP/Active Directory systems needing federated authenticationnot Fly.io
- Open-source projects and communities requiring free IAM without licensing costsnot Fly.io
- Enterprises building custom identity workflows requiring fine-grained authorisationnot Fly.io
- Teams with sufficient operational expertise to manage infrastructurenot Fly.io
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Fly.io
- Egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are
- Stopped machines still bill at $0.15 per GB of root filesystem a month, so a paused service is not a free one
- Volumes are billed on provisioned capacity rather than usage, at $0.15 per GB a month
- Reservation discounts of 40% require paying a year up front, from $36 to $1,440
- Fly Kubernetes is a separate $75 a month per cluster
- Dedicated IPv4 addresses are $2 a month each
Keycloak
- Requires self-hosted deployment and operational expertise to install, configure and maintain
- No managed cloud option provided by Red Hat; organisations must operate infrastructure themselves or use third-party distributions
- Clustering and high-availability configurations require additional operational knowledge
- Community support only; commercial support requires third-party vendors or distributions
Pricing, plan by plan
Fly.io
$29/month- Pay-as-You-Go$null/mo
- Micro VMs and persistent storage charged by usage
- FlyCTL CLI
- Unlimited users and organizations
- Serious Support$29/month
- Access to dedicated engineering team
- All Pay-as-You-Go features
- Machine Reservation Blocks$null/mo
- 40% discount on machine usage
- Requires upfront payment for savings
- Compliance Package$99/month
- HIPAA compliance
- BAAs
- SOC2 documentation
Keycloak
Free- Open-sourceFree
- Full platform functionality
- Self-hosted deployment
- Community support
Which should you pick?
Choose Fly.io if
- You need global deployment.
- You work on Web, Api, Docker.
- You also want docker support.
Choose Keycloak if
- You want to start without paying.
- You work on Self-hosted, Docker, Kubernetes, Linux, Windows, API.
Questions people ask
- Is Fly.io or Keycloak better?
- Neither clearly leads. Fly.io starts at $29/month and Keycloak at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Fly.io or Keycloak?
- Keycloak has a free tier; the other does not. Paid plans start at $29/month for Fly.io and Free for Keycloak.
- Does Fly.io or Keycloak run on more platforms?
- Fly.io runs on Web, Api, Docker. Keycloak runs on Self-hosted, Docker, Kubernetes, Linux, Windows, API.
- Can I use Keycloak for free?
- Yes. Keycloak has a free tier, so you can try it without paying. Fly.io starts at $29/month.
- What is Fly.io best used for?
- Fly.io is most often used for deploying containerised applications close to users across regions, running full stack apps and databases on managed machines. Of those, deploying containerised applications close to users across regions and running full stack apps and databases on managed machines are not what Keycloak is typically brought in for.
- What can Fly.io do that Keycloak cannot?
- Fly.io covers Global deployment, Docker support, Postgres databases, Redis support.
Answered from the vendors’ own pages
Fly.io: Is there a free tier for Fly.io?
Fly.io does not advertise a free tier. The base plan is pay-as-you-go with usage-based pricing for Micro VMs and persistent storage. All users get FlyCTL CLI, unlimited organizations, private networking, SSO, ACLs, and scoped tokens.
SourceKeycloak: What protocols does Keycloak support?
Keycloak supports OpenID Connect, OAuth 2.0 and SAML 2.0 protocols for authentication and authorisation.
SourceFly.io: How much does Fly.io Serious Support cost?
Serious Support costs 29 USD per month and provides access to a dedicated engineering team while maintaining all pay-as-you-go features for Micro VMs and storage.
SourceKeycloak: Can Keycloak integrate with existing user directories?
Yes. Keycloak supports user federation with LDAP and Active Directory systems, allowing organisations to leverage existing user directories.
SourceFly.io: What does Fly.io Compliance Package include?
The Compliance Package is 99 USD per month and includes HIPAA compliance, BAAs, and SOC2 documentation for organizations requiring compliance certifications.
SourceKeycloak: Is Keycloak free?
Yes. Keycloak is fully open-source and free to deploy and use. No licensing fees are required.
SourceFly.io: Does Fly.io offer discounts for upfront commitment?
Yes, Fly.io offers Machine Reservation Blocks with 40% discount on machine usage. This requires upfront payment but applies savings on infrastructure costs.
SourceRelated pages
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