Phase 1: MongoDB Migration - Environment Setup & Dependencies

[devin-ai-integration]

Phase 1: MongoDB Migration – Environment Setup & Dependencies

Summary

This PR implements Phase 1 of the MongoDB migration plan by adding MongoDB infrastructure and configuration alongside the existing DynamoDB setup without changing any application logic.

Changes:

• Dependencies: Add pymongo>=4.0.0 to requirements.txt (kept boto3 and all existing deps).
• Chalice config: Add MONGODB_URI to environment_variables for both local and dev stages.
• Env docs: Add .env.example documenting MONGODB_URI and the existing API_ENDPOINT.
• Helper script: Add test_mongodb_connection.py to validate local MongoDB connectivity end-to-end.

Out of scope by design: No changes to DynamoDB code and no changes to application code (e.g., app.py, chalicelib/ddb.py).

Review & Testing Checklist for Human

3–5 items

• Validate the .chalice/config.json changes: confirm adding "MONGODB_URI" for both local and dev stages is desired (dev currently points to mongodb://localhost:27017—ok for local dev, but please confirm this is correct for your dev usage).
• Install deps and sanity check: pip install -r requirements.txt should succeed cleanly with both boto3 and pymongo installed in your environment.
• Ensure DynamoDB tests still pass when the environment is configured:
  • Set AWS_DEFAULT_REGION (e.g., export AWS_DEFAULT_REGION=us-east-1) and run DynamoDB Local per README.
  • Then run pytest -vv. The current NoRegionError appears to be a pre-existing environment variable issue, not introduced by this PR.
• Confirm keeping test_mongodb_connection.py in repo is acceptable (it’s a local helper for validation only; I can move it under scripts/ or remove if not desired).
• Optional: chalice local --stage local and verify that adding MONGODB_URI does not affect existing DynamoDB behavior.

Suggested test plan:

1. Start MongoDB: sudo systemctl start mongod; ensure it listens on 27017.
2. Validate Mongo: python test_mongodb_connection.py should report successful connection and read from chat.chat.
3. DynamoDB Local: run per README, set export API_ENDPOINT=localhost and export AWS_DEFAULT_REGION=us-east-1.
4. Run tests: pytest -vv.
5. chalice local --stage local (optional) to confirm the app still behaves as before.

Notes

• No application logic was altered; this is purely additive infra/config work to prepare for MongoDB migration while preserving the DynamoDB path.
• I verified local MongoDB connectivity with pymongo and created the chat database and chat collection.
• Existing tests currently error with NoRegionError, which is an environment configuration issue (missing AWS region) and appears unrelated to these changes.
• Session: https://app.devin.ai/sessions/ce3c02b17d124a4bac404b0ce6fb2b18
• Requested by: Abhay Aggarwal (@abhay-codeium)

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