⚡ Bolt: Offload synchronous SQLite calls in FastAPI

[Adityasingh-8858]

💡 What:
Wrapped all synchronous SQLite database operations (create_transfer_record, set_agent_b, list_transfers, and get_transfer) inside backend/main.py using asyncio.to_thread.

🎯 Why:
FastAPI's asynchronous endpoints operate on a single thread event loop. Any blocking I/O calls (like executing SQLite disk queries, especially those that enforce thread locks under high volume) will block the loop, delaying all other pending concurrent network requests (e.g. standard endpoints like health checks or other active client connections). Offloading them directly improves the backend's capability to safely multiplex.

📊 Impact:
Significantly improves concurrent request handling capabilities and responsiveness. While exact metrics depend on disk I/O constraints under load, this prevents zero-concurrency bottlenecks when the database executes complex queries or awaits disk writes.

🔬 Measurement:
Verification can be handled by concurrently hitting endpoints (e.g., using pytest async concurrent mocks or standard benchmark tools like wrk or ab against the /transfers endpoints) and verifying that parallel non-database endpoints (like /health) remain responsive.

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PR created automatically by Jules for task 17486751300406044669 started by @Deepaksingh7238

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[Copilot]

Pull request overview

This PR improves FastAPI endpoint concurrency by offloading the backend’s synchronous SQLite persistence operations onto a threadpool so they don’t block the event loop.

Changes:

• Wrapped persistence.create_transfer_record(...) calls in initiate_transfer with await asyncio.to_thread(...).
• Wrapped persistence.set_agent_b(...), persistence.list_transfers(...), and persistence.get_transfer(...) with await asyncio.to_thread(...).
• Added a short Bolt/Jules note documenting the rationale for offloading synchronous DB work in async endpoints.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
backend/main.py	Offloads synchronous SQLite persistence calls via asyncio.to_thread to prevent event-loop blocking in async endpoints.
.jules/bolt.md	Documents the “offload sync DB calls from async endpoints” guidance for this repo.

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