Add a loan eligibility endpoint to an existing Flask API
Last updated: August 6, 2025
Quick Overview
Given an existing Flask application with user and loan models, add a new endpoint that checks whether a user is eligible for a loan based on their credit score, existing debt, and income. Navigate the existing codebase to understand patterns before coding.
Affirm
August 6, 202515
5
1,644 solved
Given an existing Flask application with user and loan models, add a new endpoint that checks whether a user is eligible for a loan based on their credit score, existing debt, and income. Navigate the existing codebase to understand patterns before coding.
This is Affirm's signature coding round format. Instead of a blank editor, you receive an existing Flask codebase and must extend it. The interviewer evaluates how you read unfamiliar code, follow existing patterns, and add functionality that fits naturally.
What the Interviewer Expects
- Read and understand the existing codebase structure before writing any code
- Follow the existing patterns for route definition, request validation, and error handling
- Implement the eligibility logic with clear, readable conditions
- Add proper input validation and meaningful error responses
- Write code that fits the style and conventions of the existing codebase
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you add rate limiting to this endpoint?
- How would you make the eligibility rules configurable without code changes?
- How would you add logging for audit purposes?
- How would you test this endpoint, including edge cases in eligibility logic?
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Problem Analysis
In this task, we need to add a new endpoint in an existing Flask API that determines a user's loan eligibility based on their credit score, existing debt, and income. The pattern that applies here is ...
Approach
- Understand Existing Codebase: Start by locating the Flask app and reviewing the routes defined in
app.pyor similar file. Identify how other endpoints are structured, including how they handl...
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