Async database queries in FastAPI - Mini Project: Build & Apply

Async database queries with FastAPI

📖 Scenario: You are building a simple FastAPI app that fetches user data from a database asynchronously. This helps your app stay fast and responsive even when waiting for the database.

🎯 Goal: Create a FastAPI app that uses async functions to query a mock database and return user info.

📋 What You'll Learn

Create a list of user dictionaries as mock database

Add a variable to hold the user ID to search for

Write an async function to find the user by ID

Create a FastAPI route that calls the async function and returns the user

💡 Why This Matters

🌍 Real World

Async database queries keep web apps responsive by not blocking the server while waiting for data. This is important for apps with many users or slow databases.

💼 Career

Understanding async queries and FastAPI routes is essential for backend developers building modern, scalable web APIs.

1

Create mock user data

Create a list called users with these exact dictionaries: {'id': 1, 'name': 'Alice'}, {'id': 2, 'name': 'Bob'}, and {'id': 3, 'name': 'Charlie'}.

FastAPI

# Create the list called users with 3 user dictionaries
# Your code here

Need a hint?

Use a list with dictionaries inside. Each dictionary has keys 'id' and 'name'.

2

Set user ID to search

Create a variable called search_id and set it to 2.

FastAPI

users = [
    {'id': 1, 'name': 'Alice'},
    {'id': 2, 'name': 'Bob'},
    {'id': 3, 'name': 'Charlie'}
]
# Create search_id variable and set to 2
# Your code here

Need a hint?

Just assign the number 2 to the variable named search_id.

3

Write async function to find user

Write an async function called get_user_by_id that takes user_id as a parameter. Inside, use a for loop with user to check if user['id'] == user_id. If yes, return user. If no user found, return None.

FastAPI

users = [
    {'id': 1, 'name': 'Alice'},
    {'id': 2, 'name': 'Bob'},
    {'id': 3, 'name': 'Charlie'}
]

search_id = 2

# Write async function get_user_by_id(user_id) to find user
# Your code here

Need a hint?

Use async def to define the function. Loop through users and compare IDs.

4

Create FastAPI route to return user

Import FastAPI from fastapi. Create an app instance called app. Add a route with @app.get('/users/{user_id}') that defines an async function read_user taking user_id: int. Inside, call get_user_by_id(user_id) with await and return the result.

FastAPI

users = [
    {'id': 1, 'name': 'Alice'},
    {'id': 2, 'name': 'Bob'},
    {'id': 3, 'name': 'Charlie'}
]

search_id = 2

async def get_user_by_id(user_id):
    for user in users:
        if user['id'] == user_id:
            return user
    return None

# Import FastAPI, create app, and add async route /users/{user_id}
# Your code here

Need a hint?

Remember to import FastAPI, create app, and use async def with await inside the route.