Keycloak is rapidly gaining momentum as a robust open-source identity management solution. From small startups to large-scale enterprises, its easy integration and extensive functionality make it a popular solution to handle user authentication, authorization, and access control. One of Keycloak’s primary and most beneficial concepts for scalability and multi-tenancy is the “realm.” But a pressing question among IT administrators and architects frequently arises: Is it possible to store Keycloak realms in different databases?

This detailed blog post aims to clarify the possibility, advantages, limitations, and practical considerations of splitting your Keycloak realms across separate databases.

Understanding Keycloak Realms

First, let’s clarify the fundamental concept of a “realm” within Keycloak.

What exactly is a Keycloak realm?

In Keycloak, a realm represents an isolated identity management space. Each realm essentially acts like an independent identity management unit housing its own users, roles, identity providers, themes, and configuration settings. Thus, different organizations or departments within a company often utilize separate realms for improved identity isolation, management convenience, or compliance.

Common use cases and scenarios for realms:

• Multi-tenant Applications: To segregate user identities and authentication processes for different tenants securely.
• Data Isolation and Protection: Protect sensitive data by restricting access between realms, preventing accidental or malicious cross-data exposure.
• Security and Compliance: To ensure organizational or departmental compliance with data sovereignty and regulatory standards like HIPAA, GDPR, or financial standards.

Realms ensure secure encapsulation of configurations and prevent unnecessary data leakage between different groups or applications.

Default Storage Approach in Keycloak

Before exploring separate-database options, let’s look at Keycloak’s default architecture:

Usually, Keycloak stores data (users, roles, settings) in a centralized relational database, such as PostgreSQL, MySQL, MariaDB, Oracle, or MS SQL. By default, regardless of the number of realms you have, Keycloak will store all realms within a single database instance.

Typical architecture setup:

• Single relational database.
• Multiple tables and schemas to differentiate realms logically.
• Segregation of data is logical only, not implemented physically at the database-level per realm.

Advantages of default single-database architecture:

• Simplified maintenance and easy backups.
• Centralized management of user accounts, enabling unified monitoring and administration.
• Cost-effectiveness, reducing infrastructure overhead.

Limitations of default single-database approach:

• Reduced isolation may introduce compliance or security issues for stringent industries.
• Increased dependency on a single point of failure can present a risk.
• Difficulties managing massive scaling, particularly where individual realms grow to sizable proportions.

Is it Possible to Store Realms in Separate Databases?

Keycloak users frequently ask if they can achieve physical separation of their realms into distinct databases. Unfortunately, out-of-the-box Keycloak does not support storing different realms in multiple databases directly. By design, Keycloak expects all realm data to be present within the same database instance.

Some individuals misunderstand that “multi-tenancy” equals “multi-database,” but Keycloak manages multi-tenancy logically within a single database environment.

However, while it’s not officially supported or directly achievable through Keycloak default features, there are alternative approaches, including separate Keycloak deployments or customized integration scenarios.

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Potential Solutions and Workarounds

While native multi-database support is currently unavailable (and unlikely part of future Keycloak releases), alternative strategies can satisfy your requirements:

1. Running Multiple Keycloak Instances

You can manage database isolation by deploying a separate Keycloak instance for each realm. Each Keycloak deployment would then connect independently to its own database instance.

Pros:

• Total data isolation.
• Simplified compliance and security.
• Easy independent backup and restore possibilities.

Cons:

• Increased management efforts with duplicated resources.
• Higher infrastructure cost.
• Increased operational complexity.

2. Containerization and Orchestration Approaches

Using container technology (like Docker) alongside orchestration tools (such as Kubernetes), you can spin up multiple instances of Keycloak with isolated application environments, each with independent databases.

This approach offers scalability, robust management capability, and isolation required for multi-database realms.

3. Keycloak Extensions and Third-party Solutions

Custom extension development allows deeper customization by implementing your realm-level logic and connecting through custom data stores or microservices. While highly customizable and targeted to specific scenarios, extension-based solutions may significantly increase complexity, requiring substantial developer resources and expertise.

Pros and Cons of Separate Databases per Realm

Is maintaining a different database per realm worth it? Let’s weigh a few key considerations.

Advantages:

• Increased Isolation and Security: Physically isolating user databases decreases the likelihood of cross-tenant breaches.
• Simplified Backup, Restore, and Maintenance: Easily target backups for specific customer segments without bringing down your entire Keycloak environment.
• Compliance and data privacy requirements: Better positioned to meet strict regulations requiring separation of customer or regional data.

Disadvantages:

• Infrastructure Complexity: You face a more elaborate architecture setup.
• Increased Operational Overhead: Multiple databases increase complexity regarding updates, migrations, and infrastructure management.
• Potentially Reduced Scalability: Overhead inefficiencies could reduce scalability without significant resources and planning.

Practical Considerations and Recommendations

Considering separate databases per realm fundamentally hinges on your organization’s unique requirements and environment conditions.

• Small-scale Deployments: For smaller installations, single-database, multi-realm architectures most likely suit your needs adequately and cost-effectively.
• Large-scale or Regional Operations: If data sovereignty, compliance, or customer isolation is mandatory, balancing additional complexity against strict regulations typically makes separate Keycloak deployments per realm sensible.
• Highly-Regulated Industries: Particularly in finance, health, or defense sectors, data isolation per realm is vital and physically separate databases become extremely attractive.

Critically assess regulatory standards, data privacy compliance requirements, your security model, and infrastructure resources to make a fully-informed determination.

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Real-world Case Studies/Examples

For large enterprise businesses, such as multinational financial institutions or healthcare organizations working under GDPR or HIPAA standards, divided databases per realm might be an obligation rather than a mere preference.

• International firms occasionally rely on multiple regional Keycloak instances with corresponding databases to remain compliant with diverse regional requirements (e.g., GDPR in Europe).
• Financial institutions often separate realms by financial service lines, allowing isolated auditing, monitoring, backups, and data integrity.

Real-world instances bear out the validity and viability of separate Keycloak deployments where complex compliance or security concerns dictate.

FAQs – Frequently Asked Questions:

What exactly is a Keycloak realm?

A realm in Keycloak is a logically isolated space to manage identity, authentication, authorization, roles, and users within a separate context or namespace.

Can Keycloak realms share data or configurations?

Realms typically do not share user or configuration data. However, common settings such as email configurations and identity provider setups can sometimes be standardized across realms, depending on your configuration pattern.

Does Keycloak officially support multiple databases for multiple realms?

Official Keycloak documentation does not support storing different realms in separate databases. Architectures that achieve this are either extension-based or through separate Keycloak installations entirely.

What database types does Keycloak support by default?

Keycloak supports a wide variety of relational database systems including PostgreSQL, MySQL, MariaDB, Oracle, MSSQL, among others.

Can I achieve realm isolation using a single database server but different schemas?

Though theoretically possible via custom Hibernate configurations or extensive extension development, this is not officially supported and adds significant complexity.

Are there performance implications to splitting realms into different databases?

Managing multiple databases adds complexity, possibly introducing latency, synchronization issues, increased infrastructure costs, and management overhead.

How can I migrate data if I eventually need separate databases per realm?

Keycloak has export/import functionalities. Database migration tools also enable exports/imports. Planning comprehensive data integrity and minimal downtime during migration is crucial.

Is it viable to manage different realms with separate Keycloak deployments entirely?

Yes, separate deployments work. Yet increased infrastructure maintenance, complexity, and overhead are critical considerations.

Conclusion

In summary, while Keycloak realms cannot be directly isolated across different databases in a single instance by design, there are strategic workarounds and architecture options available. Whether separate database deployments for your Keycloak realms make sense involves careful consideration of security, privacy compliance, scalability, management complexity, and cost implications.

Careful architectural planning based on your organization’s unique requirements remains crucial. When in doubt, consult official Keycloak documentation and seek professional advisement.

Call to Action (CTA):

We encourage readers to delve deeper into official Keycloak documentation or collaborate with identity management experts. Have any experiences or questions regarding Keycloak realms or multi-database scenarios? We invite your comments and discussions below to learn from shared knowledge and practical experiences.