Implement real, working microservices architecture

backend/shared/db.py

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+import os
+from sqlalchemy.orm import sessionmaker, Session
+from sqlalchemy import create_engine
+from .constants import DATABASE_URL
+
+# Database connection settings
+POOL_SIZE = int(os.getenv("DB_POOL_SIZE", "20"))
+MAX_OVERFLOW = int(os.getenv("DB_MAX_OVERFLOW", "40"))
+POOL_RECYCLE = int(os.getenv("DB_POOL_RECYCLE", "1800"))
+POOL_TIMEOUT = int(os.getenv("DB_POOL_TIMEOUT", "30"))
+
+POOL_CONFIG = {
+    "pool_size": POOL_SIZE,
+    "max_overflow": MAX_OVERFLOW,
+    "pool_recycle": POOL_RECYCLE,
+    "pool_timeout": POOL_TIMEOUT,
+    "pool_pre_ping": True,
+}
+
+def create_engine_from_url(database_url: str):
+    """Create SQLAlchemy engine from database URL."""
+    connect_args = {}
+    if database_url.startswith("sqlite"):
+        connect_args["check_same_thread"] = False
+
+    engine_kwargs = {
+        "pool_size": POOL_SIZE,
+        "max_overflow": MAX_OVERFLOW,
+        "pool_recycle": POOL_RECYCLE,
+        "pool_pre_ping": True,
+        "pool_timeout": POOL_TIMEOUT,
+    }
+
+    engine = create_engine(
+        database_url,
+        connect_args=connect_args,
+        **engine_kwargs,
+    )
+
+    return engine
+
+# Create engine - this should be called by each service with its own DATABASE_URL
+def get_engine(database_url: str = None):
+    """Get SQLAlchemy engine for the given database URL."""
+    url = database_url or DATABASE_URL
+    return create_engine_from_url(url)
+
+# Session factory - create per service
+def get_session_factory(database_url: str = None):
+    """Get session factory for the given database URL."""
+    engine = get_engine(database_url)
+    return sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+# Dependency for FastAPI - create per service
+def get_db(database_url: str = None):
+    """FastAPI dependency to get database session."""
+    SessionLocal = get_session_factory(database_url)
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()