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When it comes to building and launching innovative B2B SaaS products, advanced authentication methods such as SSO often sit in a peculiar position. They're critical to security and enterprise readiness, yet frequently relegated to "we'll deal with it later" status.

The timing of when you implement enterprise-level authentication capabilities can significantly impact your product's development velocity, security posture, and enterprise readiness.

As one developer observed bluntly on Reddit: "Wiring up auth retroactively is insanely annoying, and you will absolutely miss something."

Strategic timing decisions around authentication implementation can make or break scaling efforts.

In this article, we'll explore three distinct scenarios for implementing authentication, incorporating real-world perspectives from founders and developers who've been through these scenarios before.

Disclaimer: Throughout this article, when we refer to "authentication", we mean more advanced authentication methods that make your SaaS more enterprise-ready.

Scenario 1: Baking advanced authentication into your MVP

Every MVP needs authentication, but to which level do you take it? From simple social logins to passwordless and SSO, your MVP could have varying levels of authentication.

When advanced auth methods make sense

• You're building security-focused products
• You're explicitly targeting enterprise customers from launch

The benefits

Starting with advanced authentication baked into your MVP establishes proper security foundations from the beginning. It prevents the costly and error-prone process of retrofitting security later, establishes appropriate data access patterns from day one, and reduces technical debt related to security systems.

One Redditor captured the essence of this approach:

“think starting with auth is a good idea. If you’re still excited about the app after doing the auth you’ll know it’s an idea really worth pursuing.”

Another developer shared their personal journey: "For years I'd come up with an idea, code all the fun parts, then abandoned it when it came time to decipher the Identity docs for the 6th time."

The challenges

The early authentication approach can slow initial development velocity as your small team tackles auth complexity before proving product-market fit. The implementation complexity of enterprise features like SSO can be particularly distracting if you're racing to demonstrate core value.

As one founder put it: "People nowadays spend all their time with Auth0 and Cognito; it adds so much complexity to their application. It's just not worth dealing with it in the beginning.”

Scenario 2: Integrating authentication during core product development

When this approach makes sense

• Your product doesn't immediately serve enterprise customers but has a clear enterprise trajectory
• Your product handles sensitive data, but initial users are limited to something like a beta release

The benefits

This middle-ground approach allows you to focus on core functionality initially while planning for authentication integration as your feature set matures. You can model user permissions alongside feature development.

One developer describes their process: "I tend to start with basic auth configured through the app settings right from the beginning. This doesn't distract too much from what I actually want to build and can easily be swapped out for something more fancy such as an OAuth SSO provider or whatever is necessary."

Another noted that they would bake in the auth “instantly” after developing the app:

“Create the app, set up routing, create some components (a login page, admin page, regular page, some dummy ones if needed), then straight into setting up auth with route guards. Doing it later is a massive pain.

Another developer shared their personal journey: "For years I'd come up with an idea, code all the fun parts, then abandoned it when it came time to decipher the Identity docs for the 6th time."

The challenges

This approach requires careful architecture planning to avoid major refactoring later. You may need to pause feature development to implement authentication properly, and there's always the risk of security gaps if the implementation isn't thorough.

“I've been caught in traps where I've been excited to start a new project, only to spend days/weeks figuring out auth before being able to move onto the interesting parts.”

Scenario 3: Adding authentication after core product development

When this approach makes sense

• Product-market fit is highly uncertain
• You're not targeting enterprise customers initially
• You have very limited engineering resources (1-2 person team)

The benefits

This approach offers the fastest path to initial market validation. Your development focus remains entirely on core product functionality, and you can choose authentication solutions based on validated user needs rather than assumptions.

One developer argued for this approach: "IMO if it's a solo project and you don't have an 'auth template' to adopt that you're familiar with, start first with a user model and bolt on an auth provider later."

The real-world wake up call

The "auth comes later" approach can work for initial validation, but it comes with significant enterprise-readiness costs. One founder shared this sobering experience:

“We were essentially laughed out of the room when we showed our biggest prospect how we managed users in our legacy product. I felt really smug about my fancy hand-coded user management tooling until about 50% into the presentation when I could see an equivalently-smug look + mild sideways head shaking coming from the customer CTO. Running in-house authentication is literally a joke to many of these orgs.”

This founder continued: "Realizing that we might have lost a multi-million dollar customer over an ego trip was a bit of a wake-up call... At a certain point, it's about making money and being able to sleep at night."

Decision framework: When and how should your SaaS implement enterprise auth?

To determine the right timing and method for your authentication implementation, consider these key factors:

1. Target market alignment

If enterprise customers are in your immediate future, authentication should be a front-loaded concern. As one Redditor noted:

“Let's assume your SaaS is B2B and you anticipate having many thousands of users. Based on my experience... you'll want to implement SSO + SCIM. You want to allow your customers to bring their own auth system with them (SSO) and be able to 'sync' their users to your SaaS easily (SCIM).”

2. Security requirements vs. Development velocity

Balance your security needs against your development speed. One user shared their "just in time" authentication principle:

1. Use managed auth from day 1
2. Implement bare minimum flows
3. Only add social providers after 50+ signups
4. Never “roll your own authentication” until 10k+ users

They added: "I've wasted 20+ hours on custom auth for products nobody used."

3. Build vs. Buy assessment

Building authentication in-house might seem appealing at first, but many developers strongly advocate against it:

"Building your own Auth system is hard, like very, very hard," one developer emphasized. “I would advise you piggyback of another system until you scale to get a competent security tech team to build this architecture OR consider additional security like SMS confirmation on login?

My personal opinion is that you SHOULD build your own once you’re scaling with the right team behind it.”

Another developer with extensive experience was even more direct: "I've built a bunch of SaaS platforms over the years... and almost without fail the biggest chunk of work (especially when you get to a scale where you need external audits like PCI or ISO) ends up being diagnostics, bugfixing, and eventually replacing your auth mechanism as things evolve and standards change."

4. Risk assessment

Consider both technical and business risks. One founder put it bluntly:

“If something goes wrong and one of our customers gets breached, I don't want the investigation to wind up at a line of code in my codebase. That means I have to get involved in legal proceedings. I am completely out of the game of touching end-user passwords or MFA tokens now.”

The enterprise authentication roadmap

Based on the real-world experiences shared above and our experience with B2B SaaS companies, here's a pragmatic roadmap:

1. For pre-PMF startups: Use managed authentication from day one, but implement minimal flows. Focus on core product validation.
2. For startups finding PMF: Begin planning your enterprise-grade authentication approach. Start integrating SSO capabilities before enterprise customers demand them.
3. For scaling startups: Implement SCIM and advanced enterprise features like role-based access control and just-in-time provisioning as you target larger customers.
4. For established SaaS vendors: Consider whether your authentication capabilities are a competitive advantage or limitation. Many companies discover they're leaving money on the table with inadequate enterprise readiness.

As one developer succinctly concluded: "Auth is a well-understood problem, but easy to get wrong. Use a canned version from the start. Would you really want to develop a database system from scratch or other important pieces of infrastructure rather than the 'unique' features your application will provide users?"

Whether you choose to build or buy your authentication solution, the timing of when you tackle this challenge matters. The right approach aligns with your growth stage, target market, and available resources—allowing you to focus on what truly differentiates your product while ensuring you don't create authentication debt that comes back to haunt you when enterprise customers come knocking.

For a deeper exploration of the build vs. buy considerations when implementing SSO for your SaaS application, check out our detailed analysis.

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Sources:

[1]  At what stage do you add authentication when developing a new app? Why?

[2]  “Successful SaaS founders: How do you handle auth?”

[3]  “Running in house authentication for B2B SaaS”

Managing sessions in Go

Once authentication succeeds, you need to manage user sessions securely. Never store tokens in local storage, as it exposes them to cross-site scripting (XSS) attacks.

When advanced auth methods make sense

1. Store idToken Securely

Use an encrypted cookie for authentication tokens. Set HttpOnly and Secure flags to prevent JavaScript access.

Use an encrypted cookie for authentication tokens. Set HttpOnly and Secure flags to prevent JavaScript access.

2. Use accesstoken for Future API calls

One Redditor captured the essence of this approach:

Scenario 3: Adding authentication after core product development

When this approach makes sense

• Product-market fit is highly uncertain
• You're not targeting enterprise customers initially
• You have very limited engineering resources (1-2 person team)