Best Tech Stack for Building an API as a Solo Developer

I've shipped five different APIs over the years. Some serve mobile apps, some power SaaS products, and one is a public API that third-party developers integrate with. The stack I keep coming back to depends on one question. How performance-critical is this thing?

For most solo developers, the answer is "not very." Your API needs to be reliable, well-documented, and quick to build. It doesn't need to handle 100,000 requests per second on day one. Here's what I'd pick.

The Recommended Stack

Why This Stack Works for Solo Developers

When you're building an API alone, the framework does 80% of the heavy lifting. FastAPI gives you automatic request validation, automatic API documentation, async support, and type checking. That's four things you'd otherwise build or configure yourself.

I switched from Express.js to FastAPI about two years ago and my productivity roughly doubled. Not because Python is inherently better than JavaScript, but because FastAPI makes so many decisions for you. Request validation? Pydantic handles it. Documentation? Swagger UI is generated automatically from your type hints. Async endpoints? Just add async def.

The result is that you write less code, ship faster, and get production-quality documentation without any extra work.

Framework: FastAPI

FastAPI is the fastest-growing Python web framework for a reason. Write a function with type hints, and you automatically get request validation, serialization, and interactive API documentation. It's almost unfair how much it does for you.

Here's a real example. A typical CRUD endpoint in Express requires manually validating the request body, writing error handling, and separately maintaining API docs. In FastAPI, you define a Pydantic model and the framework handles all three.

Alternatives. Django REST Framework if you want the full batteries-included experience (admin panel, ORM, auth, everything). Express.js or Hono if you're a JavaScript developer and don't want to learn Python. Go with Gin or Echo if raw performance matters more than development speed. But for solo developers who want to ship fast, FastAPI is the sweet spot.

Database: PostgreSQL

Every API needs a database, and PostgreSQL is the safe default. It handles relational data, JSON columns, full-text search, and geospatial queries. Whatever your API needs to store, Postgres can handle it.

I've used MongoDB for APIs before, and I regretted it every time. The flexibility of schemaless documents sounds great until you're debugging inconsistent data shapes at 2 AM. Postgres with a proper schema prevents those problems.

For the ORM, I use SQLAlchemy with Alembic for migrations. It's Python-native and works perfectly with FastAPI. If you're in the JavaScript world, Prisma is the equivalent and it's excellent.

Auth: Keep It Stateless

For APIs, authentication usually means one of two things. API keys for third-party developers, or JWT tokens for your own frontends.

API keys are dead simple. Generate a random string, store a hash in your database, and check it on every request. That covers 90% of API auth needs.

JWTs work when your API serves a frontend you control. The frontend logs in, gets a token, and sends it with every request. No session storage needed on the server.

Don't start with OAuth2 unless your API genuinely needs third-party integrations. I built a full OAuth2 provider once for an API that had exactly zero third-party developers for the first year. That was wasted time.

What I'd Skip

GraphQL. For a solo developer's API, REST is simpler to build, easier to cache, and better understood by most developers. GraphQL makes sense when multiple clients need wildly different data shapes. If you're building one API for one frontend, REST wins.

Microservices. Build one API. One service. One database. One deployment. Split it up later if you actually need to, which you probably won't.

API gateways. Kong, AWS API Gateway, or similar tools add complexity you don't need. Your framework handles rate limiting, authentication, and routing. Use what's built in.

Serverless for everything. Lambda functions are great for webhooks and cron jobs. They're terrible for APIs with database connections, cold start sensitivity, or complex business logic. A simple server is easier to reason about.

Getting Started

1. Scaffold the project. Create a FastAPI project with a proper folder structure. Separate your routes, models, and business logic from day one. It takes 10 extra minutes and saves you hours later.

2. Set up PostgreSQL. Use Railway or Render's managed Postgres. Connect it with SQLAlchemy and create your first migration with Alembic.

3. Build your core endpoints. Focus on the 3-5 endpoints that matter most. Get them working, tested, and documented before adding anything else.

4. Deploy early. Push to Railway or Render. Have a live API URL you can share. Test against production, not just localhost.

5. Write a README. Your API is useless if nobody knows how to use it. FastAPI's auto-generated docs help, but a good README with example requests makes all the difference.

The best API stack for a solo developer is one that minimizes boilerplate and maximizes the time you spend on business logic. FastAPI does exactly that. Build the thing, ship it, and iterate based on what your users actually need.