Authentication sounds simple.
You check who the user is, match them to a record in your database, and let them in.
But if you get this wrong, the damage is serious. Attackers can pretend to be your users, read private data, or even steal money through account takeovers.
That is why authentication is not something you should casually build yourself.
This post explains why most developers should stop reinventing auth and instead use a dedicated authentication provider like Clerk or Keycloak.
Why You Should Stop Building Your Own Auth Flow
When you start a new app, it is easy to think authentication is just:
Sign a JWT
Store it in a cookie
Done
This works for demos and side projects. It almost never works for real products.
In a real SaaS application, authentication grows in complexity very fast. What looks simple at the start becomes a constant source of bugs, security risks, and lost time.
Here is why using an auth provider is usually the better choice.
1. Stateful Authentication Is Hard
Most production apps need stateful authentication, not just stateless JWTs.
Stateful auth lets you do things users expect, such as:
See all devices a user is logged into
Add a “Log out of all devices” button
Instantly revoke access if something looks suspicious
To support this, you need more than tokens. You need:
A session database
Fast storage like Redis
Careful logic for expiration and revocation
Consistency across your backend, frontend, and APIs
One small mistake can leave old sessions active or lock users out by accident.
Auth providers already solved this problem. You would be rebuilding years of work.
2. Social Login Is a Bigger Problem Than It Looks
Users expect “Sign in with Google, GitHub, or Twitter.”
OAuth sounds easy until you implement it yourself.
The hardest part is not redirects. It is account linking.
Example:
A user signs up with email and password.
Later, they try “Sign in with Google” using the same email.
What should happen?
Do you link the accounts?
Do you create a second user?
What if the emails match but the provider does not verify them?
If you get this wrong, you create duplicate users, broken profiles, and confusing login behavior.
Auth providers handle these edge cases every day. Most custom systems do not.
3. Security Is a Full-Time Job
When you build your own auth, you own all security risks.
That includes:
New attack patterns as they appear
Browser cookie changes and SameSite rules
Token leakage and replay attacks
Password policies and brute-force protection
Role-Based Access Control (RBAC)
Security companies have teams whose only job is to think about this 24/7.
If you cut corners to save time, you are not just saving time.
You are trading security and user trust for speed.
That is rarely a good deal.
4. Your Time Is More Valuable Than You Think
As a developer or founder, your time is limited.
You can spend weeks building a “solid” auth system.
Or you can spend those weeks building:
Your core product
Features users actually pay for
Things that make your app different
Authentication does not make your product unique.
Your idea and execution do.
Key Takeway
Use an auth provider until the cost forces you not to.
If your auth bill hits $10,000 a month, you probably have:
Millions of users
Real revenue
A strong engineering team
At that point, building custom auth might make sense.
Until then, use an API, ship faster, and sleep better.
Conclusion
Authentication is a solved problem.
Modern auth providers give you:
Strong security
Polished user experience
Advanced features with minimal code
Do not let “simple auth” turn into a weeks-long bottleneck.
Use the tools that already exist.
Focus on building the product only you can build.
But the reality is—at the end of the day, all of us have to deal with authentication in one way or another.
Whether you build the entire system yourself or not, lacking even a basic understanding can easily lead to serious mistakes.
Which parts are the most sensitive,
where developers usually get tripped up,
and what key concepts you need to know to keep the whole auth picture clear in your head—
that mental map is what I’ll cover in the next note.