Build a Full Stack AI SaaS Application in 60 Minutes

The Modern AI SaaS Stack

Building a full-stack AI SaaS application no longer requires months of development. The right combination of managed services and AI coding tools can compress what used to be weeks of work into a single focused session.

This post breaks down a production-ready stack: Next.js for the frontend and API routes, Clerk for authentication and billing, Convex for real-time data and file storage, and 11 Labs for AI voice generation. The goal is simple: establish a solid foundation, then leverage AI coding tools to accelerate everything else.

Authentication and Billing with Clerk

Clerk handles what traditionally consumes the most setup time in any SaaS: user management and monetization. Beyond standard OAuth (Google, GitHub, etc.) and email flows, Clerk's recent billing feature eliminates the complexity of Stripe integration.

Instead of managing webhooks for subscription changes, upgrade/downgrade logic, and payment failure handling manually, Clerk abstracts this into configuration. You define plans (Free, Pro, Premium), set pricing tiers with optional annual discounts, and assign feature flags to each tier. The platform handles the Stripe integration, receipt emails, and subscription state management.

For a $20/month Pro plan, Clerk takes 0.7% of transactions. The trade-off is straightforward: zero webhook maintenance, built-in email handling, and type-safe access control through the has() method that works on both frontend and backend.

Real-Time Backend with Convex

Convex serves as both database and file storage, with a killer feature: real-time sync between backend and UI without additional infrastructure. Define your schema in TypeScript, save the file, and the tables exist immediately - no migrations to run.

The platform runs your backend functions on their servers, not as Next.js routes. This separation means your API logic scales independently of your frontend deployment. For file storage, Convex accepts blobs directly - no S3 buckets or signed URLs to configure.

Authentication integrates through JWT templates. Configure the issuer domain in Clerk, add it to Convex's environment variables, and every request carries the user's identity automatically.

AI Voice Generation via 11 Labs

11 Labs provides text-to-speech with voice cloning capabilities. Their per-character billing model maps naturally to SaaS tiering: Free users get limited characters, Pro users get more, Premium gets unlimited.

Integration requires an API key with scoped permissions (good security practice) and a simple POST endpoint. The SDK returns audio streams that you can pipe directly to the client or store for later playback. Voice selection happens through voice IDs, which you can expose as dropdown options in your UI based on the user's subscription tier.

The AI Coding Workflow

The critical insight: AI coding tools work best after the foundation is set. Do not start with Cursor or Claude Code. Start with documentation, API keys, and basic project structure.

The workflow follows three phases:

Phase 1: Foundation (Manual)

• Initialize the Next.js project with TypeScript and Tailwind
• Configure Clerk middleware and providers
• Set up Convex client and schema
• Create the 11 Labs API route

Phase 2: Acceleration (AI-Assisted) Once the plumbing exists, use Cursor's agent mode or Claude Code to generate components. The AI understands your existing Clerk setup, Convex schema, and API structure. Prompt for a landing page with navigation, pricing section, and FAQ - it creates components that respect your authentication context.

Phase 3: Refinement (Mixed) Use AI for targeted fixes: "Convert inline styles to Tailwind," "Fix dark mode text contrast," or "Add error handling to this TypeScript interface." The fix-in-place feature handles syntax errors and type mismatches without rewriting entire files.

Gating Features by Subscription

Clerk's has() method enables granular access control without custom middleware. Check user.has({ plan: "pro" }) in your Next.js API routes to protect endpoints, or use it in server components to conditionally render UI.

On the backend, guard your 11 Labs route:

const hasPro = await auth.has({ plan: "pro" });
if (!hasPro) return new Response("Unauthorized", { status: 403 });

On the frontend, conditionally show navigation items or entire components based on the same check. Users without access see upgrade prompts; users with access see the feature. Clerk handles the subscription state synchronization automatically.

File Storage and History

With Convex file storage, saving generated audio requires minimal code. Create an HTTP action that accepts a form data payload containing the audio blob, text metadata, and format. Store the blob using storage.store(), get back a storage ID, and write the metadata to your database table.

To display user history, create a Convex query that filters by the authenticated user's ID and returns recent files. The Convex React client provides useQuery hooks that update in real-time - no polling or refresh logic required.

Deployment Path

When ready for production:

• Deploy the Next.js app to Vercel
• Push Convex to production (toggles between dev/prod environments in the dashboard)
• Enable live mode in Clerk (switches from test transactions to real payments)

The entire stack provisions without custom infrastructure. Authentication, billing, database, file storage, and AI integration all run as managed services.

Watch the Video