Technology · head to head
etcd vs Keycloak
etcd
Technology
A distributed key-value store using Raft consensus, built for cluster coordination rather than application data.
- From
- On request
- Free plan
- No
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: etcd it is sized for coordination data, not application data: the default backend quota is 2 GB and 8 GB is the documented recommended maximum, and exceeding it puts the cluster into a NOSPACE alarm where it accepts no writes until an operator compacts, defragments and clears the alarm by hand.; 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 etcd and Keycloak actually diverge.
Identical on both: pricing model (open-source), 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 etcd
- Raft consensus
- Linearizable reads
- Transactions
- Leases
- Watches
- MVCC revision history
- Role-based access control
- Snapshot backup and restore
Only in Keycloak
Nothing recorded that etcd does not also cover.
What people use each for
The jobs each tool is most often brought in to do.
etcd
- Storing Kubernetes cluster state, which is what the overwhelming majority of etcd deployments are doingnot Keycloak
- Leader election and distributed locking in a home-grown scheduler or control plane, using leases and transactionsnot Keycloak
- Service discovery and dynamic configuration where readers need to be notified of changes rather than poll for themnot Keycloak
- Coordinating failover in a clustered database, as Patroni does for PostgreSQLnot Keycloak
Keycloak
- Organisations requiring self-hosted identity infrastructure for compliance or data residencynot etcd
- Companies with existing LDAP/Active Directory systems needing federated authenticationnot etcd
- Open-source projects and communities requiring free IAM without licensing costsnot etcd
- Enterprises building custom identity workflows requiring fine-grained authorisationnot etcd
- Teams with sufficient operational expertise to manage infrastructurenot etcd
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
etcd
- It is sized for coordination data, not application data: the default backend quota is 2 GB and 8 GB is the documented recommended maximum, and exceeding it puts the cluster into a NOSPACE alarm where it accepts no writes until an operator compacts, defragments and clears the alarm by hand.
- Every write is replicated and fsynced before acknowledgement, so cluster performance is bounded by the slowest disk in it; a member on network-attached storage with high fsync latency causes leader elections and cluster-wide latency spikes that look like network problems and are not.
- Adding members increases availability but reduces write throughput, because each write must reach a larger quorum; you run three or five members for fault tolerance, and increasing capacity means faster hardware rather than more nodes.
- There is no sharding and no multi-tenancy, so isolating workloads means running separate clusters, each with its own quorum, certificates, backup schedule and upgrade path, and that operational multiplication is often unexpected.
- Running it yourself is a real job: periodic compaction and defragmentation, snapshot backups you have actually rehearsed restoring, and rotation of both peer and client TLS certificates, none of which happens automatically outside a managed Kubernetes service.
- Losing quorum is not self-healing; recovering a cluster that has lost a majority means restoring from a snapshot and accepting that everything written since that snapshot is gone, which makes backup frequency a data-loss budget decision rather than a routine setting.
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
etcd
On requestNo published plan breakdown. See the etcd review.
Keycloak
Free- Open-sourceFree
- Full platform functionality
- Self-hosted deployment
- Community support
Which should you pick?
Choose Keycloak if
- You want to start without paying.
- You work on Self-hosted, Docker, Kubernetes, Linux, Windows, API.
Questions people ask
- Is etcd or Keycloak better?
- Neither clearly leads. etcd starts at On request and Keycloak at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, etcd or Keycloak?
- Keycloak has a free tier; the other does not. Paid plans start at On request for etcd and Free for Keycloak.
- Does etcd or Keycloak run on more platforms?
- etcd runs on Web. 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. etcd starts at On request.
- What is etcd best used for?
- etcd is most often used for storing kubernetes cluster state, which is what the overwhelming majority of etcd deployments are doing, leader election and distributed locking in a home-grown scheduler or control plane, using leases and transactions, service discovery and dynamic configuration where readers need to be notified of changes rather than poll for them, coordinating failover in a clustered database, as patroni does for postgresql. Of those, storing kubernetes cluster state, which is what the overwhelming majority of etcd deployments are doing and leader election and distributed locking in a home-grown scheduler or control plane, using leases and transactions are not what Keycloak is typically brought in for.
- What can etcd do that Keycloak cannot?
- etcd covers Raft consensus, Linearizable reads, Transactions, Leases.
Answered from the vendors’ own pages
etcd: Can I use etcd as an application database?
No. It is designed for metadata and coordination, with a recommended maximum store size of around 8 GB, no sharding and a write path deliberately optimised for durability rather than throughput. Application data belongs in a database built for it.
Keycloak: What protocols does Keycloak support?
Keycloak supports OpenID Connect, OAuth 2.0 and SAML 2.0 protocols for authentication and authorisation.
Sourceetcd: How many members should a cluster have?
Three for most cases, five where you need to survive two simultaneous failures. Always an odd number, because an even-sized cluster gains no additional fault tolerance while making quorum harder to reach.
Keycloak: 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.
Sourceetcd: What happens when the store fills up?
The cluster raises a NOSPACE alarm and stops accepting writes, becoming effectively read-only. Recovery requires compacting old revisions, defragmenting each member and then explicitly disarming the alarm, all done by an operator.
Keycloak: Is Keycloak free?
Yes. Keycloak is fully open-source and free to deploy and use. No licensing fees are required.
Sourceetcd: Why is my etcd cluster slow or unstable?
Almost always disk latency. Because every write is fsynced before acknowledgement, slow or shared storage causes heartbeat timeouts, leader elections and cascading latency. Local SSDs with low fsync latency are effectively a requirement.
etcd: How does it compare with Consul or ZooKeeper?
All three provide consensus-backed coordination. etcd has the simplest data model and the Kubernetes ecosystem behind it; Consul bundles service discovery, health checking and a service mesh; ZooKeeper is older, JVM-based and still common under Kafka and Hadoop-era systems.
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