Keycloak Multitenancy Approaches for SaaS

What is Multitenancy in Identity Management?

In today’s cloud‑native applications, Keycloak multitenancy is essential when you need to serve multiple organisations, departments, or clients from a single platform. This pattern is core to our Multi‑Tenant Platform Development work. Multitenancy in SaaS identity management lets each tenant keep its own user base and configuration inside the same Keycloak instance.

Keycloak is an open‑source identity and access management solution that offers SSO, authorization, and identity management. It supports OAuth2, OpenID Connect (OIDC), and SAML, making it ideal for cloud‑native identity needs.

In this post we explore the approaches we use at Afriq Silicon for implementing Keycloak multitenancy (OIDC). The guide assumes basic familiarity with Keycloak terminology.

Separate Realms Per Tenant

This is the most straightforward way to achieve strong isolation. Each tenant receives its own Realm, a separate namespace for users, roles, clients, and authentication flows.

Advantages

• Full isolation lets you customise branding, login flows, and policies per tenant.
• Realm ID can serve as the tenant identifier in downstream databases.

Drawbacks

• Managing many realms adds operational overhead and increases resource consumption.

Shared Realm with Tenant‑Specific Roles or Groups

A single realm serves all tenants, while differentiation is done through Roles or Groups. Users are assigned roles or placed in groups that correspond to their tenant.

Advantages

• Simpler administration and lower resource use.
• Centralised configuration eases updates.

Drawbacks

• Isolation is weaker; you must implement detailed authorization rules to keep tenant data separate.

Partitioning with Realms and Clients

Create separate Clients for each tenant within a single realm. Each client defines its own redirect URIs, roles, and login settings.

Advantages

• Client‑level isolation keeps most settings separate while sharing the realm’s core configuration.
• Easier to provision new tenants via the Admin REST API.

Drawbacks

• Shared realm settings can still lead to cross‑tenant leakage if not carefully managed.

Identity Provider Federation for Multitenancy

Keycloak can delegate authentication to external providers per tenant (e.g., LDAP, Azure AD). This lets tenants use their own identity sources while you retain centralised access control.

Advantages

• Flexibility to integrate existing directories.
• Reduces the need to migrate user data into Keycloak.

Drawbacks

• Adds complexity and potential points of failure in the authentication chain.

Best Practices for Implementing Keycloak Multitenancy

1. Automate tenant provisioning – Use the Keycloak Admin REST API to create realms, clients, and users programmatically.
2. Plan for scaling – Large‑scale deployments benefit from clustering and horizontal scaling, especially with the realm‑per‑tenant model.
3. Enforce isolation with RBAC – Define tenant‑specific roles and policies to keep data separate while enabling SSO within each tenant.
4. Monitor per tenant – Integrate with observability tools such as Prometheus and Grafana to trace performance and errors to individual tenants.
5. Consider procurement and team size – Choose the approach that matches your organisation’s procurement rules and engineering capacity; a shared‑realm model often suits thin teams with limited budgets.

Ready to build a secure, scalable multi‑tenant SaaS? Contact Afriq Silicon to discuss how we can design, implement, and operate your Keycloak‑based identity solution.