README.md

Case Study: Temporary File Upload Handling

Problem	Solution	Impact
Multi-step form uploads using JSON + multipart risk data loss and concurrency issues.	Temporary storage + Redis metadata (file_id, path, TTL); finalize to permanent storage on submit.	Reliable multi-step uploads, concurrent-safe, simple integration with existing forms.

Key points:

• Temporary files stored under /tmp/uploads/<user_id> with TTL
• Metadata in Redis allows validation and concurrent workflows
• Finalization uploads file to permanent storage (e.g., GCS) and cleans temp data

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Problem

Frontend needed to upload user files in multi-step forms using:

• JSON requests for form data
• multipart/form-data for files

Challenges:

• prevent data loss
• support concurrent multi-request uploads
• validate before final submission

Solution

• Add temporary backend storage (/tmp/uploads/<user_id>)
• Store metadata in Redis (file_id, path, MIME, TTL, user_id)
• Flow:
  1. User selects file → POST /files/temp (multipart/form-data)
  2. File saved locally + metadata in Redis
  3. Final form submit → backend validates file, uploads to permanent storage (GCS), deletes temp file

Impact

• Reliable multi-step uploads
• Supports concurrent users
• Simple integration with existing forms

Lessons Learned

• Temporary storage + metadata system is simple and reliable
• Decouples file handling from form submission
• Allows safe multi-request workflows