Hello Marc-André,
From SQLAlchemy 1.2 Documentation:
"Connection Pool Configuration
The Engine returned by the create_engine() function in most cases has a QueuePool integrated, pre-configured with reasonable pooling defaults. If you’re reading this section only to learn how to enable pooling - congratulations! You’re already done. "
SQLAlchemy handles connection pooling and closing in the flexible environment, as documented on the "Using Cloud SQL for MySQL"
page. In other words, connection pooling is enabled by default in this case.