fix: release database connections immediately after auth instead of holding during LLM calls
Authentication was using Depends(get_session) which holds a database connection
for the entire request lifecycle. For chat completions, this meant connections
were held for 30-60 seconds while waiting for LLM responses, despite only needing
the connection for ~50ms of actual database work.
With a default pool of 15 connections, this limited concurrent chat users to ~15
before pool exhaustion and timeout errors:
sqlalchemy.exc.TimeoutError: QueuePool limit of size 5 overflow 10 reached,
connection timed out, timeout 30.00
The fix removes Depends(get_session) from get_current_user. Each database
operation now manages its own short-lived session internally:
BEFORE: One session held for entire request
──────────────────────────────────────────────────
│ auth │ queries │ LLM wait (30s) │ save │
│ CONNECTION HELD ENTIRE TIME │
──────────────────────────────────────────────────
AFTER: Short-lived sessions, released immediately
┌──────┐ ┌───────┐ ┌──────┐
│ auth │ │ query │ LLM (30s) │ save │
│ 10ms │ │ 20ms │ NO CONNECTION │ 20ms │
└──────┘ └───────┘ └──────┘
This is safe because:
- User model has no lazy-loaded relationships (all simple columns)
- Pydantic conversion (UserModel.model_validate) happens while session is open
- Returned object is pure Pydantic with no SQLAlchemy ties
Combined with the telemetry efficiency fix, this resolves connection pool
exhaustion for high-concurrency deployments, particularly on network-attached
databases like AWS Aurora where connection hold time is more impactful.
3f133fad56