Fix: Return HTTP 404 for missing users instead of HTTP 500

[mw-middleware-labs-sandbox]

Problem

The user_profile() endpoint was raising KeyError exceptions when users requested non-existent user profiles, resulting in:

• HTTP 500 (Internal Server Error) instead of HTTP 404 (Not Found)
• Error tracking alerts for expected validation scenarios
• Polluted error logs with non-critical events

Root cause: Line 78 in flask/app.py raised KeyError for missing users

Evidence: Middleware Alert ID 30146661 captured 4 exceptions for requests to user6 and user7

• Trace IDs: 87d91b0053a48f58314fe5da15969183, ccd931d37c1f50d48b9dd318dfaad3ad, 6af879c070957ded75792488460679fa, d4e957f8384ae2b3ebf82a187e0cb110
• Alert: https://sandbox.middleware.io/alerts/rules?ruleid=144047&alert_id=30146661

Solution

• Added abort to Flask imports
• Check if username exists in user_data before lookup
• Return HTTP 404 with descriptive message for missing users
• Removed unreachable error handling code

Impact

✅ Returns semantically correct HTTP 404 for missing users
✅ Prevents error tracking alerts on expected validation failures
✅ Improves API adherence to REST best practices
✅ Reduces noise in error logs

Testing

Test with:

curl -i http://localhost:5000/user/nonexistent
# Should return HTTP 404 instead of HTTP 500

Changes

• Line 10: Added abort to Flask imports
• Lines 63-67: Replaced KeyError exception logic with proper 404 handling using abort(404, ...)

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Created By

Name: Bajrang
Email: bajrang.ostwal+sandbox@middleware.io