Build vs. buy: How to approach SSO for your SaaS app

Every B2B organization building for enterprise customers faces a pivotal decision: should you build Single Sign-On (SSO) in-house or adopt a third-party solution?

Most teams assume SSO is just another login screen. In reality, it’s a protocol-heavy, edge-case-ridden infrastructure layer that affects user experience, security, scalability, and engineering velocity.

This guide is designed to help product and engineering leaders understand the true scope of building SSO, hidden operational burdens, and when it makes strategic sense to buy.

What is enterprise SSO?

‍Enterprise-grade authentication allows users to access multiple applications using one set of credentials. It integrates with identity providers (IdPs) like Okta, Entra (Azure AD), and Google Workspace, streamlining authentication while meeting complex security and compliance requirements.

An effective SSO implementation improves user experience, reduces password fatigue, and helps close enterprise deals.

What you need to build for enterprise SSO

Core SSO components

Enterprise SSO isn’t just one simple login feature. Beyond the core authentication process, you'll need to handle complexities such as multi-tenancy, integrations with various identity providers (IdPs), attribute mapping, and robust admin tools. Here’s a detailed breakdown of all the components you need to build in-house:

These components collectively represent a significant long-term commitment.

Timeline and resource commitment

To build and operationalize enterprise-grade SSO, organizations should plan for a sustained multi-quarter effort involving dedicated senior engineering resources. The table below provides a clear view of the effort and team size required:

Hidden operational burdens

‍Implementing SSO is not a "launch and forget" scenario. Teams often underestimate the ongoing operational responsibilities that pull resources away from core product development. The table below highlights these hidden yet significant recurring tasks:

Learn more : The Strategic Role of Authentication in B2B SaaS Applications

The case for rolling your own auth

Now that we've looked at what's required for building auth, we'll also briefly look at the benefits of rolling your own.

1. Control and customization

Without a doubt, rolling your own SSO solution offers complete control over the authentication process, allowing for customization that precisely fits your organization's specific needs. This is particularly important for unique or highly specialized use cases, where a custom SSO implementation might be the best approach.

2. Integration with legacy systems

For organizations with complex, legacy systems, a custom-built SSO might be necessary to ensure seamless integration that might not be possible with off-the-shelf solutions.

3. Long-term cost benefits

For large organizations with multiple product offerings, the initial high investment in rolling your own custom SSO might pay off over time. Depending on the size of your organization and the number of users, the cost of licensing third-party SSO solutions can be substantial depending on the vendor. Further, owning your infrastructure reduces dependency on a specific vendor’s technology, pricing changes, and terms of service. This can provide greater business continuity and stability.

Strategic alternative: Scalekit

Scalekit simplifies enterprise SSO by handling all the complexity and overhead for you. Here's what Scalekit offers out-of-the-box:

Enterprise SSO

Business velocity and customer onboarding

Security and compliance

Developer experience

ROI: Build in-house vs. Scalekit

Comparing strategic impact: Deciding whether to build or buy SSO comes down to understanding how each choice affects your business strategy, resource allocation, and speed-to-market. The following table compares critical factors of both approaches.

Build vs. buy decision framework

This framework helps you determine whether to build internally or adopt a managed solution like Scalekit. 

Bottomline: Build or buy?

Scalekit provides enterprise-grade SSO without the heavy lifting, allowing your engineers to stay focused on product innovation:

• Complete SAML/OIDC implementation
• Support for multiple IdPs, accounting for the quirks of each
• Ready-to-deploy, secure, and compliant infrastructure
• Minimal operational overhead
• Fast deployment, freeing up your team

Choose Scalekit to simplify enterprise SSO, so your team can focus on what they do best.

Deciding whether to build or buy your SSO? Sign up for a Free Forever account with Scalekit and start with enterprise-ready SSO infrastructure instantly. Need help evaluating your options? Book time with our auth experts.

FAQs

How does enterprise SSO impact B2B SaaS engineering velocity?

Building enterprise SSO in house requires significant time, often taking twelve to sixteen weeks of dedicated engineering effort. This timeline covers core SAML and OpenID Connect protocols, multi tenant routing, and security hardening. By choosing a managed provider like Scalekit, teams can deploy production ready authentication in less than three days. This shift allows developers to focus on core product innovation rather than maintaining complex identity infrastructure. It ultimately eliminates the long term burden of protocol updates, certificate management, and cross provider interoperability testing that typically bogs down internal roadmaps.

Why is multi tenant configuration difficult for internal auth teams?

Multi tenancy introduces complex requirements such as organization specific metadata exchange and isolated session handling. Each enterprise customer brings unique identity provider configurations, requiring your system to resolve login routes based on email domains or custom subdomains. Without a robust architecture, managing these individual certificate rotations and attribute mappings becomes a manual support nightmare. Scalekit simplifies this by providing a self serve admin portal. This allows customers to configure their own connections, reducing the operational load on your backend engineers while ensuring secure, isolated authentication flows for every unique organization you serve.

What are the hidden costs of maintaining SAML certificate rotations?

Security certificates for SAML assertions eventually expire, and missing a renewal window causes immediate login failures for enterprise users. Building an automated system for certificate monitoring, rotation, and revocation requires dedicated DevOps and backend resources. These hidden operational tasks persist long after the initial launch, often consuming several hours of engineering time every week. Scalekit automates the entire lifecycle of certificate management. By handling expiry checks and rotation workflows out of the box, it ensures business continuity and prevents high priority support escalations that distract your team from building revenue generating features.

How does third party SSO support SOC2 and ISO compliance?

Enterprise grade authentication must meet rigorous security standards, including assertion signature validation and replay protection. Auditors for SOC2 or ISO certifications scrutinize how your application handles sensitive identity data and audit logs. Building these compliant flows from scratch involves extensive security hardening and documentation. Scalekit provides a production ready infrastructure that is already optimized for compliance requirements. It includes built in encryption, detailed auth event logging, and secure token handling. This pre configured security posture accelerates your audit preparation and gives CISOs confidence that the authentication layer meets modern enterprise infosec expectations.

How should architects approach authentication for AI agent interactions?

As B2B applications evolve to support AI agents and Machine to Machine workflows, traditional session based auth is insufficient. Architects must implement robust Machine to Machine or Agent to Agent authentication patterns using client credentials or specialized tokens. While the provided guide focuses on human SSO, the underlying principle of offloading complex protocol management remains vital. Using a centralized provider ensures that your AI agents can securely authenticate across different service boundaries without building bespoke security logic for every integration. This unified approach to identity management helps maintain a consistent security perimeter for both human users and automated software agents.

Why is a self serve admin portal critical for SSO?

Without a customer facing configuration UI, every SSO setup becomes a manual task for your support or engineering teams. This manual onboarding creates friction and delays in closing enterprise deals. A self serve portal empowers customer IT admins to upload their own metadata, test configurations, and map custom attributes independently. Scalekit includes a white labeled admin interface out of the box, enabling faster customer onboarding and reducing time to value. This functionality transforms a technical hurdle into a seamless user experience, allowing your sales team to move faster without being blocked by technical implementation details.

Do different identity providers require unique implementation logic?

Yes, major identity providers like Okta, Microsoft Entra, and Google Workspace often exhibit subtle differences in how they handle SAML assertions or OIDC claims. These quirks lead to unexpected edge cases, such as broken relay states or mismatched audience URIs. Testing against every possible provider requires a massive library of test cases and dedicated QA simulators. Scalekit abstracts these differences by providing a unified API that handles the nuances of each identity provider. This ensures a consistent login experience across your entire customer base without requiring your engineers to become experts in every specific identity protocol variation.

Can Scalekit help manage machine to machine authentication at scale?

Modern B2B SaaS architectures often require Machine to Machine communication for background tasks or API integrations. Implementing secure patterns like Dynamic Client Registration or managed client credentials is essential for protecting these service to service flows. While building these capabilities in house adds months of development time, leveraging a specialized authentication platform ensures that your Machine to Machine tokens are issued and validated using industry best practices. This centralized control provides visibility into how different services interact, making it easier to rotate secrets and monitor for unauthorized access across your entire distributed architecture or microservices environment.

When is it strategically better to build SSO in house?

Building an in house SSO solution makes sense only if identity infrastructure is a core differentiator for your product. If you have a surplus of senior engineering bandwidth and a need for highly specialized, legacy integrations that off the shelf tools cannot support, a custom build might be appropriate. However, for most B2B organizations, authentication is a utility rather than a competitive advantage. In these cases, buying a managed solution like Scalekit is the strategic choice. It minimizes initial investment, reduces ongoing operational costs, and ensures your team remains focused on the unique features that actually drive business growth.