From b389fe3e23037f26a9d1d63e78c08890c65c3d22 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 12 Jul 2026 23:36:05 +0000
Subject: [PATCH] Offload bcrypt crypto operations to threadpool in auth.py

Offloads `bcrypt.hashpw` and `bcrypt.checkpw` in `backend/auth.py` to `starlette.concurrency.run_in_threadpool`. Changes `verify_password` and `get_password_hash` to be `async def`. This prevents CPU-bound crypto tasks from blocking the event loop when processing `register`, `login`, and `setup_initial_admin` endpoints, improving concurrency and throughput.

Co-authored-by: benpiper <4343814+benpiper@users.noreply.github.com>
---
 .jules/bolt.md  |  3 +++
 backend/auth.py | 12 +++++++-----
 backend/main.py |  6 +++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index e6d39e6..1768cd2 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -16,3 +16,6 @@
 ## 2024-06-28 - Optimize array lookups in high-frequency React event handlers
 **Learning:** Even if data is pre-processed/memoized (like cached `parsedTimestamps`), performing an O(N) linear search on that array inside a high-frequency event handler (like `<video onTimeUpdate>`, which fires multiple times per second) can cause UI stuttering for large arrays.
 **Action:** When searching sorted arrays (like ordered video timestamps) in high-frequency event loops, replace linear iteration loops with an O(log N) binary search to minimize main thread blocking and ensure smooth UI execution.
+## YYYY-MM-DD - Offload bcrypt to threadpool
+**Learning:** CPU-bound operations like `bcrypt.hashpw` block the event loop in `async` endpoints in FastAPI.
+**Action:** Use `starlette.concurrency.run_in_threadpool` and change synchronous functions to `async def` when performing CPU-heavy crypto operations.
diff --git a/backend/auth.py b/backend/auth.py
index f958845..979284a 100644
--- a/backend/auth.py
+++ b/backend/auth.py
@@ -6,6 +6,7 @@
 import bcrypt
 import jwt
 from sqlalchemy.ext.asyncio import AsyncSession
+from starlette.concurrency import run_in_threadpool
 from sqlalchemy import select, func
 from models import User
 from database import get_db
@@ -22,11 +23,12 @@
 
 oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")
 
-def verify_password(plain_password, hashed_password):
-    return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))
+async def verify_password(plain_password, hashed_password):
+    return await run_in_threadpool(bcrypt.checkpw, plain_password.encode('utf-8'), hashed_password.encode('utf-8'))
 
-def get_password_hash(password):
-    return bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt()).decode('utf-8')
+async def get_password_hash(password):
+    hashed_bytes = await run_in_threadpool(bcrypt.hashpw, password.encode('utf-8'), bcrypt.gensalt())
+    return hashed_bytes.decode('utf-8')
 
 def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
     import uuid
@@ -65,7 +67,7 @@ async def initialize_admin_from_env(db: AsyncSession):
     if admin_password_hash:
         hashed = admin_password_hash
     elif admin_password:
-        hashed = get_password_hash(admin_password)
+        hashed = await get_password_hash(admin_password)
     else:
         return False
 
diff --git a/backend/main.py b/backend/main.py
index f637f4a..7c30bd5 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -244,7 +244,7 @@ async def register(user: UserCreate, db: AsyncSession = Depends(get_db)):
     user_count = result.scalar()
     
     is_first_user = user_count == 0
-    hashed_password = get_password_hash(user.password)
+    hashed_password = await get_password_hash(user.password)
     db_user = User(
         email=user.email, 
         hashed_password=hashed_password,
@@ -267,7 +267,7 @@ async def register(user: UserCreate, db: AsyncSession = Depends(get_db)):
 @app.post("/api/auth/login")
 async def login(user: UserLogin, db: AsyncSession = Depends(get_db)):
     db_user = await get_user_by_email(db, user.email)
-    if not db_user or not verify_password(user.password, db_user.hashed_password):
+    if not db_user or not await verify_password(user.password, db_user.hashed_password):
         raise HTTPException(status_code=401, detail="Incorrect email or password")
     
     if not db_user.is_approved:
@@ -320,7 +320,7 @@ async def setup_initial_admin(user: UserCreate, db: AsyncSession = Depends(get_d
     if not user.email or not user.password:
         raise HTTPException(status_code=400, detail="Email and password required")
 
-    hashed_password = get_password_hash(user.password)
+    hashed_password = await get_password_hash(user.password)
     admin_user = User(
         email=user.email,
         hashed_password=hashed_password,