fix : scope interview experience idempotency dedup to submitting user or clientKey

[tmdeveloper007]

Summary of What Has Been Done

Changed the interview experience deduplication lookup in backend/controllers/interviewExperienceController.js to scope on (idempotencyKey, userId) for authenticated users and (idempotencyKey, clientKey) for anonymous users.

Updated backend/models/InterviewExperience.js to replace the single-field unique index with two compound partial unique indexes: { idempotencyKey: 1, userId: 1 } and { idempotencyKey: 1, clientKey: 1 }.

Updated backend/tests/interviewExperienceController.unit.test.js to reflect the new compound dedup filter in the existing retry test.

Changes Made

• backend/controllers/interviewExperienceController.js: dedup findOne now uses scoped filter; concurrent retry handler also uses scoped filter
• backend/models/InterviewExperience.js: compound unique indexes with partial filters
• backend/tests/interviewExperienceController.unit.test.js: updated assertion to expect { idempotencyKey, clientKey }

Impact it Made

Prevents one user from retrieving another user's full interview submission by re-using the same idempotency key. Proper per-user/per-client isolation for deduplication.

Closes #1795
Closes #1926

Note: Please assign this PR to the tmdeveloper007 account.

Looks good to me. Ready to merge.

[coderabbitai]

Caution

Review failed

The pull request is closed.

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📥 Commits

Reviewing files that changed from the base of the PR and between 206d384 and 5b5fce0.

📒 Files selected for processing (3)

• backend/controllers/interviewExperienceController.js
• backend/models/InterviewExperience.js
• backend/tests/interviewExperienceController.unit.test.js

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📝 Walkthrough

Walkthrough

Interview experience idempotency checks now scope duplicate submissions to the authenticated user or anonymous clientKey. Matching partial compound indexes enforce the same ownership boundaries, and retry tests verify client-scoped lookup.

Changes

Interview experience idempotency scope

Layer / File(s)	Summary
Ownership-scoped uniqueness indexes backend/models/InterviewExperience.js	The model uses separate partial compound unique indexes for (idempotencyKey, userId) and (idempotencyKey, clientKey).
Scoped duplicate handling backend/controllers/interviewExperienceController.js, backend/tests/interviewExperienceController.unit.test.js	Initial duplicate checks and concurrent duplicate-key recovery use the authenticated user or anonymous clientKey. The retry test verifies the client-scoped query.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• Canopus-Labs/PrepPilot#1375: Refines interview-experience idempotency logic across the controller, model indexes, and tests.
• Canopus-Labs/PrepPilot#1641: Extends interview-experience lookups and indexes to authenticated users and anonymous clientKeys.
• Canopus-Labs/PrepPilot#1803: Implements author-scoped lookups, race handling, and compound indexes.

Suggested reviewers: karanunique

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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