Caching strategies in FastAPI - Mini Project: Build & Apply

Caching Strategies with FastAPI

📖 Scenario: You are building a simple FastAPI web service that returns user profile data. To improve performance, you want to add caching so repeated requests for the same user ID return cached data instead of recomputing it.

🎯 Goal: Build a FastAPI app that caches user profile data in memory using a dictionary. The app should return cached data if available, otherwise generate and store it.

📋 What You'll Learn

Create a dictionary called cache to store cached user profiles.

Create a variable called cache_expiry_seconds set to 60 to define cache duration.

Write a function get_user_profile that checks the cache and returns cached data if valid, or generates new data and caches it.

Add a FastAPI route /user/{user_id} that calls get_user_profile and returns the profile.

💡 Why This Matters

🌍 Real World

Caching is used in web services to reduce repeated work and speed up responses, improving user experience and reducing server load.

💼 Career

Understanding caching strategies is important for backend developers to optimize API performance and scalability.

1

Create the cache dictionary

Create a dictionary called cache that will store cached user profiles with their timestamps.

FastAPI

# Create a dictionary called cache to hold cached profiles
# Your code here

Need a hint?

Use cache = {} to create an empty dictionary.

2

Add cache expiry configuration

Create a variable called cache_expiry_seconds and set it to 60 to define how long cached data is valid in seconds.

FastAPI

cache = {}
# Create cache_expiry_seconds variable and set it to 60
# Your code here

Need a hint?

Use cache_expiry_seconds = 60 to set the cache duration.

3

Write the caching logic function

Write a function called get_user_profile that takes user_id as input. It should check if user_id is in cache and if the cached data is not expired. If valid, return cached data. Otherwise, generate new profile data as a dictionary with user_id and name as 'User {user_id}', store it in cache with the current timestamp, and return it. Use time.time() for timestamps.

FastAPI

cache = {}
cache_expiry_seconds = 60
import time

# Write get_user_profile(user_id) function with caching logic
# Your code here

Need a hint?

Check if user_id is in cache. If yes, check timestamp. If expired or missing, create new profile and store with timestamp.

4

Add FastAPI route to serve cached profiles

Import FastAPI and create an app instance called app. Add a route /user/{user_id} using @app.get that calls get_user_profile with user_id and returns the result.

FastAPI

cache = {}
cache_expiry_seconds = 60
import time
from fastapi import FastAPI

# Create FastAPI app instance
# Add route /user/{user_id} that returns get_user_profile(user_id)
# Your code here

Need a hint?

Use app = FastAPI() to create the app. Use @app.get("/user/{user_id}") to define the route.