How I Implemented Auth & Payments in My SaaS
When building a SaaS as a solo developer, authentication and payments are the two features that feel the most intimidating—and the most critical.
If you get them wrong:
Users can’t log in
Payments fail
Trust is lost immediately
In this post, I’ll break down how I implemented authentication and payments, the decisions I made, and the mistakes I avoided while keeping things simple and scalable.
- The Goals (Before Writing Any Code)
Before implementation, I defined clear goals:
Secure authentication (without building it from scratch)
Simple onboarding (email + social login)
Reliable payments (monthly & yearly plans)
No fake analytics or dark patterns
Easy plan upgrades and downgrades
As a solo dev, maintainability > cleverness.
- Authentication: What I Needed Requirements
Email/password login
OAuth (Google, GitHub)
Secure session handling
User profile management
Password recovery
My Key Decision
I avoided rolling my own auth.
Why?
Security risks
Time-consuming
Easy to get wrong
Instead, I used a managed authentication system that provides:
JWT-based sessions
Built-in OAuth
Row-level security
Email verification
This allowed me to focus on product features, not security edge cases.
- Auth Flow (High Level)
Here’s the simplified flow:
User signs up (email or OAuth)
Auth provider creates a user ID
User record is created in my database
Session token is stored securely
User is redirected to dashboard
Key Lesson
Never trust the frontend alone—always validate sessions on the backend.
- User Profiles & Access Control
After authentication, I created a separate user profile table:
Why separate?
Auth handles identity
My database handles product data
Each user profile stores:
User ID (linked to auth)
Plan type (free / paid)
Feature access flags
Created date
This made feature gating very straightforward.
- Payments: The Harder Part
Payments introduce real-world complexity:
Failed payments
Partial upgrades
Duplicate charges
User confusion
What I Needed
One-time payments (no forced autopay)
Monthly and yearly plans
Simple upgrade logic
Payment status tracking
- Payment Flow (Simplified)
Here’s how I implemented it:
User clicks “Upgrade”
Payment modal opens
Payment is processed
Backend verifies payment
User plan is updated
Features unlock instantly
Important Rule
Never unlock features before verifying payment on the backend.
- Feature Gating Logic
Instead of checking plans everywhere, I used centralized feature flags.
Example logic:
Free → limited access
Paid → unlock specific tabs
Expired → downgrade automatically
This avoids:
UI inconsistency
Security loopholes
Duplicate logic
- Mistakes I Almost Made (So You Don’t) ❌ Building custom auth
Too risky, too slow.
❌ Unlocking features on frontend only
Anyone can bypass frontend checks.
❌ Forcing subscriptions
Users prefer transparency and control.
❌ Mixing auth data with product data
Creates long-term maintenance issues.
- What I’d Improve Next
If I were doing this again, I’d:
Add better audit logs
Improve error messaging during payment failures
Add clearer plan comparison before checkout
But for an MVP, this setup is stable, secure, and scalable.
- Final Thoughts
Authentication and payments don’t need to be complex to be reliable.
As a solo developer:
Use managed services
Keep logic centralized
Optimize for clarity
Avoid premature abstractions
If you’re building a SaaS, get these two things right early—it saves months later.
💬 Your Turn
How did you implement auth and payments in your SaaS?
Did you build it yourself or use managed services?
Let’s compare approaches 👇
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