# Micro-SaaS Stack: Supabase, Stripe & SadaSend Guide

_By Tayyab Mughal, Founder & Chief Architect · 26 September 2026 · 3 min read_

> How to build a modern micro-SaaS with Supabase Auth, Stripe webhooks, and SadaSend transactional email. Complete architecture blueprint and code recipes.

Building a SaaS in 2026? Here is how to architect authentication with Supabase, payments with Stripe, and transactional delivery with SadaSend with zero rate limits.

## The modern micro-SaaS trinity: Supabase, Stripe, and SadaSend

In 2026, solo founders and small engineering teams can ship full-scale SaaS applications without managing dedicated backend infrastructure. The winning trifecta has consolidated around three specialized engines: Supabase for Postgres data and authentication, Stripe for global payment processing, and SadaSend for transactional email delivery.

Each engine operates independently through webhooks and scoped credentials. However, wiring them together often causes subtle production bottlenecks: Supabase Auth defaults to a restrictive 2 emails/hour rate limit, and Stripe webhook handlers frequently suffer connection timeouts if synchronous email calls block worker execution.

By routing Supabase Auth through SadaSend custom SMTP and dispatching Stripe invoice receipts via asynchronous edge HTTP requests, you achieve low-latency execution with zero dropped customer notifications.

## Architecture Breakdown: Authentication, Billing & Notification Flow

| Pipeline Event | Trigger Source | Execution Layer | SadaSend Integration |
| --- | --- | --- | --- |
| User Signup & Magic Link | Supabase Auth UI | Postgres GoTrue Engine | Custom SMTP Relay (smtp.sadasend.com:587) |
| Checkout & Subscription | Stripe Checkout | Next.js 15 Server Action | REST API (POST /emails) with Idempotency-Key |
| Invoice & Failed Payment | Stripe Webhooks | Deno Edge Function | REST API with Dead-Letter Queue (DLQ) Fallback |
| Staging & Preview Tests | Vercel Preview PR | Vitest E2E Harness | Hardware Recipient Allowlist (*@company.com) |

## Production Stripe Webhook Dispatcher (TypeScript & Next.js)

Here is a battle-tested Next.js Route Handler verifying Stripe webhook signatures and triggering instant transactional receipts via SadaSend.

```typescript
import { headers } from 'next/headers';
import { NextResponse } from 'next/server';
import Stripe from 'stripe';

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!, { apiVersion: '2025-01-27.acacia' as any });

export async function POST(req: Request) {
  const body = await req.text();
  const signature = (await headers()).get('stripe-signature');

  if (!signature) {
    return NextResponse.json({ error: 'Missing stripe signature' }, { status: 400 });
  }

  let event: Stripe.Event;
  try {
    event = stripe.webhooks.constructEvent(body, signature, process.env.STRIPE_WEBHOOK_SECRET!);
  } catch (err: any) {
    return NextResponse.json({ error: `Webhook signature verification failed: ${err.message}` }, { status: 400 });
  }

  if (event.type === 'invoice.payment_succeeded') {
    const invoice = event.data.object as Stripe.Invoice;
    const customerEmail = invoice.customer_email;

    if (customerEmail) {
      await fetch('https://api.sadasend.com/emails', {
        method: 'POST',
        headers: {
          'Authorization': `Bearer ${process.env.SADASEND_API_KEY}`,
          'Content-Type': 'application/json',
          'Idempotency-Key': `stripe-invoice-${invoice.id}`,
        },
        body: JSON.stringify({
          from: 'billing@mail.yourdomain.com',
          to: customerEmail,
          subject: `Invoice Paid: #${invoice.number ?? invoice.id}`,
          html: `<h2>Payment Confirmed</h2><p>Your subscription payment of $${(invoice.amount_paid / 100).toFixed(2)} was successful.</p>`,
          tags: ['billing', 'stripe', 'invoice'],
          source: 'api',
          agent_name: 'StripeWebhookProcessor',
        }),
      });
    }
  }

  return NextResponse.json({ received: true });
}
```

## Supabase Auth SMTP Configuration in 60 Seconds

To uncap your authentication magic links and password reset OTPs:

- Log in to your Supabase Project Dashboard and open Project Settings -> Authentication.
- Scroll to SMTP Settings and enable the Custom SMTP toggle.
- Set Sender Email to your verified domain (e.g. auth@mail.yourdomain.com) and Sender Name to your product.
- Set Host to smtp.sadasend.com and Port to 587.
- Set Username to apikey and Password to your SadaSend API Key (e.g. sada_live_...), then click Save.

## Preventing Database Seeds from Leaking in Preview Environments

When testing locally or in Vercel preview branch deployments, never use your live production SadaSend API key.

Provision a dedicated Staging API key in the SadaSend dashboard configured with a Recipient Allowlist (e.g. *@yourcompany.com). Even if your local Postgres seed populates 1,000 dummy customer profiles, any accidental dispatches will be stopped at the gateway.

---

_Tags: Supabase, Stripe, Micro-SaaS, Next.js, Architecture_