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40 Advanced FastAPI Coding Challenges for Senior Developers

Prepare for your next FastAPI interview with 40 real-world coding challenges designed for experienced developers.

Core Concepts
Data Structures and Algorithms
System Design
Coding and Debugging

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Core Concepts

Data Structures and Algorithms

System Design

Coding and Debugging

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40 Advanced FastAPI Coding Challenges for Senior Developers

Identify Elite FastAPI Talent in Minutes

Core Concepts

Implement a FastAPI endpoint with proper dependency injection that validates JWT tokens and extracts user claims for authorization. Handle token expiration and invalid signatures gracefully.

Create a FastAPI background task system that processes uploaded files asynchronously, tracks progress using Redis, and sends webhook notifications upon completion. Include error handling and retry logic.

Design a FastAPI middleware that implements rate limiting per API key with sliding window algorithm, stores state in Redis, and returns appropriate headers (X-RateLimit-Remaining, X-RateLimit-Reset).

Implement a FastAPI WebSocket endpoint that supports real-time chat with message broadcasting, user presence tracking, and automatic reconnection handling. Use connection pooling and handle disconnections gracefully.

Create a FastAPI endpoint with advanced query parameter validation including regex patterns, custom validators, and dependent fields. Implement pagination with cursor-based navigation for large datasets.

Implement a FastAPI dependency that manages database transactions with proper connection pooling, automatic rollback on errors, and context manager support for nested transactions.

Design a FastAPI response caching system using Redis with cache invalidation strategies (TTL, tag-based), conditional requests (ETag), and cache warming for frequently accessed endpoints.

Implement a FastAPI streaming response endpoint that processes large CSV files chunk-by-chunk, applies transformations, and streams results without loading entire file into memory.

Create a FastAPI service that implements circuit breaker pattern for external API calls, with configurable failure thresholds, timeout handling, and automatic recovery with exponential backoff.

Implement a FastAPI endpoint with multi-part file upload validation that checks file types, scans for malware signatures, enforces size limits, and generates secure storage paths with collision prevention.

Data Structures and Algorithms

Implement an LRU (Least Recently Used) cache in FastAPI with GET and PUT endpoints. What's the time complexity?

Create a FastAPI endpoint that finds all pairs in an array that sum to a target value. Optimize for large datasets.

Implement a sliding window maximum endpoint that returns the maximum value in each window of size k from an array.

Design a FastAPI endpoint that implements a min-stack supporting push, pop, and getMin operations in O(1) time.

Create an endpoint that detects if a linked list has a cycle and returns the node where the cycle begins.

Implement a trie (prefix tree) with FastAPI endpoints for insert, search, and prefix matching operations.

Design an endpoint that merges k sorted arrays into one sorted array efficiently.

Implement a FastAPI endpoint that finds the longest substring without repeating characters.

Create an endpoint that implements binary search on a rotated sorted array to find a target element.

Design a FastAPI endpoint that implements a priority queue with custom priority values and returns top N elements.

System Design

Design a scalable URL shortener service using FastAPI. What are the key architectural components and how would you handle high traffic?

How would you design a real-time notification system with FastAPI supporting WebSockets for millions of concurrent users?

Design a rate-limiting middleware for FastAPI that works across distributed instances. Discuss algorithms and implementation strategies.

Design a distributed task queue system using FastAPI and Celery. How would you handle task prioritization, retries, and monitoring?

How would you implement a multi-tenant SaaS application with FastAPI ensuring data isolation and performance?

Design a content delivery and caching strategy for a FastAPI-based API serving media files. How would you handle cache invalidation?

Design an event-driven microservices architecture using FastAPI. How would you ensure consistency and handle distributed transactions?

How would you design a search and filtering system for FastAPI with full-text search, faceted filtering, and real-time indexing?

Design a file upload and processing pipeline with FastAPI handling large files, virus scanning, and asynchronous processing.

Design an API versioning strategy for FastAPI that supports multiple versions simultaneously while minimizing code duplication.

Coding and Debugging

Write a FastAPI endpoint that accepts a nested list and returns it flattened. How would you handle type validation?

Create a FastAPI middleware that logs the execution time of each request and identify performance bottlenecks. How would you debug slow endpoints?

Implement a FastAPI endpoint that checks if a string is a palindrome, handling Unicode characters correctly. What edge cases should you consider?

How would you implement custom exception handlers in FastAPI to return consistent error responses? Show an example with validation errors.

Write a FastAPI dependency that implements request rate limiting using Redis. How would you test this dependency?

Demonstrate how to use Python's memory profiler to identify memory leaks in a FastAPI application. What tools would you use in production?

Implement monkey patching in FastAPI to modify third-party library behavior. When is this appropriate and what are the risks?

Create a FastAPI endpoint that reverses a string efficiently while preserving Unicode grapheme clusters (e.g., emojis with modifiers). How does this differ from simple string reversal?

How would you debug a FastAPI application that's experiencing intermittent 500 errors in production? Walk through your debugging process.

Write a FastAPI background task that processes items from a queue with error handling and retry logic. How would you ensure tasks don't get lost?