How to Swap Any Provider in A2SaaS

One of the most common questions about boilerplates: "What if I want to use a different provider?"

Maybe you prefer Auth.js over Clerk. Maybe your company already uses SendGrid instead of Resend. Maybe you want Supabase instead of Neon.

A2SaaS is designed for exactly this. Here's how.

The Abstraction Philosophy

Most boilerplates hard-wire their providers. Clerk imports scattered across dozens of files. Stripe logic intertwined with business logic. Changing anything means a major refactor.

A2SaaS takes a different approach: abstraction layers.

Your app code talks to abstractions. The abstractions talk to providers. Swap the provider, keep the abstraction, and your app code doesn't change.

Auth: The Adapter Pattern

Authentication is abstracted through src/lib/auth/. Your app uses these functions:

import { getCurrentUser, getUserId } from "@/lib/auth";

// In any server component or API route
const user = await getCurrentUser(); // { id, email, name, imageUrl }
const userId = await getUserId(); // Just the ID

Under the hood, there's an adapter (src/lib/auth/adapters/clerk.ts) that implements these functions using Clerk. Want to use Auth.js instead?

1. Create src/lib/auth/adapters/authjs.ts
2. Implement the same interface
3. Update the export in src/lib/auth/index.ts

Your app code—every getCurrentUser() call—stays exactly the same.

The auth adapter interface is simple:

interface AuthAdapter {
  getCurrentUser(): Promise<AuthUser | null>;
  getUserId(): Promise<string | null>;
}

Implement those two functions for your provider, and you're done.

Email: Just a Function

Email is even simpler. The send functions in src/lib/emails/index.ts use Resend, but they're just functions:

export async function sendWelcomeEmail(email: string, name: string) {
  await resend.emails.send({
    from: siteConfig.email.from,
    to: email,
    subject: `Welcome to ${siteConfig.name}`,
    react: WelcomeEmail({ name }),
  });
}

To swap to SendGrid, Postmark, or any other provider:

1. Install their SDK
2. Update the send functions to use the new client
3. Keep the function signatures the same

The webhook handlers that call sendWelcomeEmail() don't care what's inside. They just call the function.

Database: Connection String Swap

Drizzle ORM connects to PostgreSQL via a connection string. A2SaaS uses Neon, but Drizzle works with any Postgres database.

To switch to Supabase:

1. Create a Supabase project
2. Get the connection string
3. Update DATABASE_URL in your environment

That's it. Your schema, queries, and relations all work exactly the same. Drizzle doesn't care where the database lives.

For PlanetScale (MySQL), you'd need to update the schema syntax slightly (PlanetScale doesn't support foreign keys the same way), but the Drizzle query patterns remain identical.

What Stays the Same

When you swap a provider, these things don't change:

• Your app code — Pages, components, API routes
• Your business logic — Validation, workflows, calculations
• Your database schema — Tables, relations, queries
• Your tests — (If you have them)

What changes:

• One adapter file — The provider-specific implementation
• Environment variables — API keys, connection strings
• Maybe middleware — Auth middleware is provider-specific

Skills for Swapping (Coming Soon)

We're building Claude Code skills to make provider swaps even easier:

• /swap-auth — Walk through replacing Clerk with Auth.js
• /swap-email — Switch from Resend to SendGrid
• /swap-db — Move from Neon to Supabase

Run the skill, answer a few questions, and Claude handles the file changes. No manual find-and-replace.

Want to request a skill? Open an issue on GitHub.

Why This Matters

Vendor lock-in is real. Pricing changes. Services shut down. Your needs evolve.

Building with abstraction layers means you're never stuck. You chose Clerk today because it was convenient. If you need to switch tomorrow, you can—without rewriting your app.

That's the A2SaaS philosophy: give you a solid foundation, but never trap you in it.

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TL;DR: A2SaaS abstracts auth, email, and database connections. Swap providers by changing one file, not fifty.