Why We Built 5 Products on FastAPI + Next.js (and Would Do It Again)

March 31, 2026 | 8 min read The Stack Decision That Shapes Everything Choosing a tech stack when you are a small team is one of those decisions that feels reversible but really is not. Sure, you can theoretically rewrite everything later. But in practice, whatever you pick on week one is what you are building on for the next two years. The frameworks you choose determine how fast you ship, how easy it is to hire (or onboard friends), and how much time you spend fighting your tools instead of building features. We are a group of friends from Tennessee building SaaS products under Obsidian Clad Labs. We have shipped five products on the same stack: FastAPI on the backend, Next.js on the frontend, PostgreSQL for the database. After a year of building, here is why we would make the same choice again, and what we would do differently. Why FastAPI for the Backend FastAPI is a Python web framework built on top of Starlette and Pydantic. It is async by default, has automatic OpenAPI documentat