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This project exposes three main areas of configuration: the MongoDB connection (where and how the app connects to your database), the FastAPI app metadata (title, version, and Swagger UI groupings), and the uvicorn server startup options (port, hot-reload, and host binding). All three are handled through a small number of files that are straightforward to adjust before deploying to a new environment.

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MongoDB Connection

The entire database connection is defined in a single line inside app/config/db.py: 
from pymongo import MongoClient

mong_conn = MongoClient()
Calling MongoClient() with no arguments is equivalent to MongoClient("mongodb://localhost:27017/"). This default is fine for local development where MongoDB is installed and running on the same machine. The application accesses two collections through this connection object:
Collection referenceDatabaseCollection
mong_conn.local.userlocaluser
mong_conn.local.tasklocaltask

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Connecting to a Remote Host

To point the app at a remote MongoDB server, replace the no-argument call with a full connection URI: 
from pymongo import MongoClient

# Remote host on default port
mong_conn = MongoClient("mongodb://host:27017/")

# With authentication
mong_conn = MongoClient("mongodb://username:password@host:27017/")

# MongoDB Atlas (cloud)
mong_conn = MongoClient("mongodb+srv://username:password@cluster.mongodb.net/")
After changing the MongoClient call, also update the database name in every controller that references mong_conn.local.* — for example, change mong_conn.local.user to mong_conn.myapp.user.
MongoDB’s local database is a special system database. It is never replicated across nodes in a replica set and is not backed up by most managed database services. Using it for application data means your records will not survive a replica failover or a standard mongodump backup. For any environment beyond a single-developer local machine, create a dedicated database (e.g., myapp_db) and update the collection references in app/controllers/user.py and app/controllers/task.py accordingly.

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FastAPI App Metadata

The FastAPI() constructor in main.py accepts metadata that appears in the auto-generated OpenAPI schema and Swagger UI: 
from fastapi import FastAPI
from app.config.docs import api_tags

app = FastAPI(
    title='FASTAPI + MongoDB',
    description='Learning FastAPI with MongoDB ...',
    version='2025.0.1.0',
    openapi_tags=api_tags
)
ParameterCurrent valuePurpose
title'FASTAPI + MongoDB'Displayed as the API name in Swagger UI and ReDoc
description'Learning FastAPI with MongoDB ...'Shown below the title in the API docs
version'2025.0.1.0'API version string in the OpenAPI spec
openapi_tagsapi_tagsControls endpoint grouping in Swagger UI
The api_tags list is imported from app/config/docs.py: 
api_tags = [
    {
        'name': 'User',
        'description': 'The user CRUD'
    },
    {
        'name': 'Task',
        'description': 'The tasks CRUD'
    }
]
Each entry in api_tags corresponds to a tags value set on an APIRouter. When a router declares tags=['User'], every endpoint registered on that router is grouped under the User section in Swagger UI with the description text from this list. Add a new entry here whenever you introduce a new resource router.

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Running the Server

The application is served by uvicorn, an ASGI server. Run it from the project root directory (the folder containing main.py). Basic start (default port 8000): 
uvicorn main:app
Development mode with auto-reload on port 5000: 
uvicorn main:app --reload --port 5000
FlagEffect
--reloadWatches source files for changes and automatically restarts the server. Use only during development — it adds overhead.
--port 5000Binds the server to port 5000 instead of the default 8000.
--host 0.0.0.0Binds to all network interfaces, making the server accessible from other machines on the same network.
A successful startup prints output similar to: 
INFO:     Uvicorn running on http://127.0.0.1:5000 (Press CTRL+C to quit)
INFO:     Started reloader process [12345] using WatchFiles
INFO:     Started server process [12346]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

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Interactive API Docs

FastAPI automatically generates two interactive documentation interfaces at no extra configuration cost:

Swagger UI

Available at /docs. Provides a full interactive interface where you can inspect every endpoint, view request/response schemas, and execute live requests directly from the browser.

ReDoc

Available at /redoc. Renders a clean, read-only reference view of the OpenAPI spec — useful for sharing API documentation with consumers who do not need to run requests.
Use /docs during development. The Try it out button on each endpoint lets you send real requests to your running server and inspect raw responses without needing a separate tool like Postman or curl. The api_tags groupings from app/config/docs.py keep the User and Task endpoints neatly separated so the interface stays easy to navigate as the API grows.

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