Stack to launch a SaaS in 90 days without piling up tech debt

The decisions you keep and the ones you break later. Specifically for founders racing to first paying customer in a quarter.

Launching a SaaS in 90 days is realistic if you make the boring decisions correctly and resist the urge to optimize before you have signal. What follows is the stack we use with clients in that race against the clock.

Frontend + Backend in a single framework

Next.js or Remix. No microservices, no GraphQL yet. Next App Router, Server Components for data fetching, Server Actions for mutations. One repo, one deploy, one team. This saves two months easily over a separate React + API setup.

Auth via provider, not rolled in-house

Clerk, Auth0, or Supabase Auth. You do not want to spend three weeks implementing OAuth, MFA and password recovery when a provider gives it to you for $25/month for your first 1000 users. Migrating later is trivial; rolling it from scratch up front loses you a sprint.

Database: PostgreSQL

A single relational database. No Mongo or DynamoDB on day one — those are optimizations for problems you do not have yet. Postgres handles native JSON, full-text search, vector search (pgvector). It serves several million users without breaking a sweat. Supabase, Neon or RDS — whichever, but Postgres.

Payments: Stripe with Billing

Stripe Billing handles subscriptions, trials, prorations, upgrades, automatic dunning and invoicing. Building the equivalent on MercadoPago or anything else takes months. If your market is LATAM, consider Stripe + a local complement for Latin American payment methods — but the billing core goes in Stripe.

Transactional + marketing email

Resend or Postmark for transactional. Loops or Customer.io for sequences. Avoid SendGrid in 2026 if you can — deliverability has dropped.

What will become debt in 12 months if you skip it early

Logging and observability from day one: Sentry for errors, Axiom or Logflare for logs, PostHog or Plausible for analytics. SaaS metrics instrumented from day one: signups, activation, churn, MRR. Shared types between frontend and backend (end-to-end TypeScript with Zod for validation).

What IS acceptable debt at 90 days

Full E2E tests, i18n, real multi-tenancy, dark mode, native mobile app, WCAG AA accessibility. All of that waits until product-market-fit is confirmed.

How we help at Athrun Data Intelligence

We build SaaS under this model with a dedicated squad. Free 30-min diagnostic to tell you if your idea is buildable in 90 days and what stays out of the MVP.