Stop! Don't Roll Your Own Authentication (Probably)

So, you’re building a new application, maybe a SaaS product, maybe an MVP. One of the first hurdles is user management: sign-up, login, password resets. The temptation is strong for many developers: “I can build this myself!”

Resist the Temptation

For the vast majority of products, especially in the early and growth stages, building your own authentication system is a significant drain on resources, offers little competitive advantage, and is fraught with security risks.

Let’s break down why.

Your Users Don’t Care (About Your Custom Auth)

Nobody signs up for your product because you have a clever, home-brewed authentication system. They sign up for the core value your product provides. Authentication is a necessary gateway, but it’s not the destination. Spending precious development cycles on building login screens, password hashing, token management, and email verification is time not spent on building the features that actually attract and retain users.

Note

No investor or user is impressed that you built your own auth. They’re impressed if your product solves their problem effectively. Authentication is plumbing; focus on the house.

The MVP Trap: Zero to Few Users

If you have an MVP with zero users, building custom auth is premature optimization of the highest order. Your primary goal is to validate the core product idea.

Recommendation: Use a third-party service to get authentication working in hours or days, not weeks or months.

Auth0

Firebase Auth

Clerk

Supabase Auth

AWS Cognito

Okta

The Growth Fallacy: Free to Paid Transition

You’ve got some traction, maybe a mix of free and potentially paying users. Now you think, “Okay, now I need robust, custom auth to handle subscriptions!”

Hold on. You mentioned a critical scenario: “the moment you tried to roll out a subscription your application dies your users left”. If users leave the instant you ask for payment, the problem isn’t your authentication system. The problem is likely product-market fit or your value proposition for the paid tier. Building a complex, custom authentication system won’t fix that.

Caution

Investing heavily in complex infrastructure like custom auth before validating your paid model makes potential failure much more costly. Fail fast, learn, and pivot if necessary. Don’t let auth become an expensive anchor.

Spending, say, 50% of your time building and managing auth that users ultimately won’t pay to use is a recipe for burnout and wasted investment.

The Deceptive Complexity of “Simple” Authentication

“It’s just login and password reset, right?” Wrong. Modern, secure, and user-friendly authentication is incredibly complex. What starts as a simple form quickly balloons. Consider the pieces involved:

Core Backend Logic

• DB connection management
• Securely accepting user input
• Input validation (format, strength)
• DB interactions (storing credentials)
• Secure password hashing (bcrypt, Argon2)
• Session management / Token generation (JWT)
• Secure cookie/localStorage handling
• Route protection middleware

Application Infrastructure

• Application routing logic
• API endpoint security
• Architectural patterns (MVC, etc.)
• Reliable email sending (verification/resets)
• Environment variable management (secrets!)
• Testing frameworks and tools
• Web server/framework specifics
• Robust debugging and logging

Real-World Security & Features

• Social Logins (OAuth2 / OIDC)
• OpenID Connect Standards
• Public key management (JWKS)
• Enterprise Federation (SAML)
• Correct OAuth2 flows
• Secure Refresh Tokens
• Short-lived Access Tokens
• Multi-Factor Authentication (MFA)
• Password leak detection
• Account recovery flows
• Rate limiting / Brute-force protection
• Security logging & auditing
• Compliance (GDPR, SOC2, etc.)

Security is Paramount

Authentication and authorization code is security-critical. A single mistake in hashing, token validation, or session management can lead to catastrophic data breaches, destroying user trust and potentially your business. Dedicated providers have teams of security experts focused only on this. Don’t underestimate the risk.

Building and maintaining all of this correctly, securely, and reliably is a full-time job for a dedicated team, not a side-task for your product developers.

When is Custom Auth Justified? The Rare Exceptions

Okay, are there any scenarios where building your own makes sense? Yes, but they are rare and typically apply to companies operating at a scale or with requirements most startups and SaaS products don’t have:

1. Massive Scale from Day One

Launching with millions of active users or hundreds of thousands of immediate paying customers where third-party costs might become prohibitive, and you have the expert team.

2. Core Business is Identity

Your company’s primary product is an identity platform or offers unique authentication mechanisms as a core competitive feature.

3. Extreme Customization/Regulatory Needs

Highly specific, complex, or niche regulatory/technical requirements unmet by existing providers (verify this carefully, providers are flexible).

For everyone else, the answer is almost certainly: Use a managed authentication service.

Conclusion: Focus on Your Strengths

Key Takeaway

Building a successful product is hard enough. Don’t make it harder by reinventing the wheel for a complex, security-critical component like authentication. Leverage the expertise, security, and features of dedicated providers. Focus your time, energy, and resources on building the unique value proposition of your product – that’s what your users actually care about.