We Replaced a Custom SSO with Keycloak Across 8 Applications: Lessons Learned
For years, our authentication platform worked... until it didn't.
Like many companies, we started with a custom Single Sign-On (SSO) solution. It was flexible at first, but as the number of applications grew, so did the maintenance costs, security concerns, and technical debt.
Recently, we migrated our authentication ecosystem to Keycloak, connecting 8 enterprise applications into a single identity platform.
Here are some of the biggest lessons we learned.
Why We Decided to Migrate
Our custom SSO had several challenges:
Authentication logic duplicated across applications
Difficult user and role management
Inconsistent security policies
Complex password recovery flows
Increasing maintenance costs
Limited scalability
Eventually, maintaining the platform became more expensive than replacing it.
Why Keycloak?
After evaluating different Identity Providers, Keycloak offered everything we needed:
Open Source
OpenID Connect (OIDC)
OAuth 2.0
SAML support
Multi-factor Authentication
Role-Based Access Control
Identity Federation
Social Login support
High scalability
Most importantly, it allowed us to centralize authentication without rewriting every application.
The Migration Strategy
Instead of performing a "big bang" migration, we moved one application at a time.
Each application was integrated with Keycloak while the remaining systems continued using the legacy authentication.
This approach significantly reduced deployment risk.
Biggest Challenges
Some unexpected issues included:
Legacy applications with incompatible authentication flows
Different user databases
Token validation across multiple frameworks
Session synchronization
Existing API integrations
Fortunately, Keycloak's flexibility made it possible to solve these problems with minimal impact on end users.
Results
After the migration we achieved:
Centralized authentication
Simplified user administration
Improved security
Standard OAuth2/OpenID Connect implementation
Easier onboarding of new applications
Reduced maintenance effort
The migration also made future integrations much faster.
Final Thoughts
Authentication is one of those systems that companies often postpone modernizing.
However, once the number of applications starts growing, adopting a standard Identity Provider becomes a strategic decision rather than a technical one.
If you're maintaining a custom authentication platform, it may be worth evaluating whether it's time to migrate.
About the Author
I'm a Software Architect with more than 20 years of experience building enterprise software, cloud platforms, AI solutions, and system integrations.
At Intway, we help companies modernize legacy systems, develop custom software, implement secure authentication platforms, and build AI-powered business solutions.
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