Problem Summary: My Flask application processes files successfully on the backend, but frontend requests consistently receive HTTP 409 "Conflict" errors. The backend completes processing (confirmed by logs), but responses never reach the frontend.

Evidence Backend Works:

• Application runs perfectly when tested locally

• Railway deployment logs show successful processing:

INFO: Starting BATCHED transaction processing for 94 transactions
INFO: Batch extracting vendors for 78 transactions...
INFO: Batch vendor extraction complete - got 70 results
INFO: Batch classification complete - got 49 results

Evidence of Infrastructure Issue:

• HTTP 409 errors in browser Network tab for /api/bank-cc-exporter endpoint

• Frontend timeout errors despite backend completing successfully

• Issue persists regardless of request complexity (tried both individual and batched API calls)

• Same codebase works locally without any issues

Technical Details:

• Flask app with gunicorn: --timeout 300 --workers 1 --threads 8

• Typical request: POST with file upload, processes for ~60 seconds, returns JSON

• Frontend timeout set to 120 seconds

• Backend processing completes in ~60 seconds (confirmed by logs)

What I've Tried:

• Increased frontend timeout to 2 minutes

• Simplified backend processing logic

• Verified no database conflicts (no database operations in code)

• Confirmed OpenAI API calls complete successfully

Question: Are there Railway-specific request size limits, timeout configurations, or load balancer settings that could cause HTTP 409 conflicts for file processing endpoints that take 60+ seconds to complete?