What should I use for a lightweight SaaS app with authentication?

For a lightweight SaaS app with authentication, a good default stack is:

• Frontend: Next.js
• Auth: Clerk, Auth.js (NextAuth), or Supabase Auth
• Backend/API: Next.js API routes or a small Node/Express service
• Database: Postgres
• ORM: Prisma
• Hosting: Vercel for frontend, Supabase/Neon/Railway for Postgres

Best simple choices by situation

1. Fastest to build

• Next.js + Clerk + Supabase/Neon + Prisma
• Good if you want auth handled for you and minimal setup.

2. Cheapest and very lightweight

• Next.js + Supabase
• Supabase gives you auth, database, and storage in one place.

3. More control / more portable

• Next.js + Auth.js + Postgres + Prisma
• Great if you want to own the auth flow and keep vendor lock-in low.

My recommendation

If you want the best balance of speed and simplicity: Next.js + Clerk + Neon Postgres + Prisma

If you want one platform doing most of the work: Next.js + Supabase

Why this works well for SaaS

• Easy login/signup/password reset
• Supports organizations/teams if you need B2B later
• Postgres scales well for subscriptions, users, and billing data
• Prisma makes schema changes simple

If you want, I can suggest a stack based on:

1. solo founder / MVP
2. B2B SaaS with teams
3. open-source or self-hosted
4. low-cost startup