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From Zero Course: Build a Task Manager API

Verified status as of March 28, 2026. Runtime note: FastFN auto-installs function-local dependencies from requirements.txt / package.json; host runtimes are required in fastfn dev --native, while fastfn dev depends on a running Docker daemon. Welcome to the FastFN "From Zero" course! If this is your first time building a function, start here. This tutorial assumes zero prior knowledge of FastFN.

What are we building?

Over the next 4 parts, we will build a complete Task Manager API from scratch. You will learn how to: 1. Create your first endpoint and return data. 2. Handle dynamic routes (like /tasks/1) and read request bodies. 3. Manage environment variables and function configuration. 4. Return rich responses like HTML or custom headers.

Prerequisites

You only need the FastFN CLI installed. - Portable mode (recommended): Docker Desktop running. - Native mode: fastfn dev --native (requires OpenResty + runtimes installed on the host).

Everything in this tutorial works identically in both modes.

Learning Path

  1. Part 1: Setup and Your First Route
  2. Part 2: Routing and Data
  3. Part 3: Configuration and Secrets
  4. Part 4: Advanced Responses

Let's get started!

Flow Diagram

flowchart LR
  A["Client request"] --> B["Route discovery"]
  B --> C["Policy and method validation"]
  C --> D["Runtime handler execution"]
  D --> E["HTTP response + OpenAPI parity"]

Objective

Clear scope, expected outcome, and who should use this page.

Validation Checklist

  • Command examples execute with expected status codes
  • Routes appear in OpenAPI where applicable
  • References at the end are reachable

Troubleshooting

  • If runtime is down, verify host dependencies and health endpoint
  • If routes are missing, re-run discovery and check folder layout

See also

Last reviewed: March 28, 2026 · Docs on fastfn.dev