Efficient session variable server-side caching with Python+Flask

Scenario:

• Major web app w. Python+Flask
• Flask login and Flask.session for basic session variables (user-id and session-id)

Flask.session and limitations? (Cookies)

• Cookie based and basically persist only at the client side.

• For some session variables that will be regularly read (ie, user permissions, custom application config) it feels awkward to carry all that info around in a cookie, at every single page request and response.

Database is too much?

• Since the session can be identified at the server side by introducing unique session id at login, some server-side session variable management can be used. Reading this data at the server side from a database also feels like unnecessary overhead.

Question

• What is the most efficient way to handle the session variables at the server side?

Perhaps that could be a memory-based solution, but I am worried that different Flask app requests could be executed at different threads that would not share the memory-stored session data, or cause conflicts in case of simultaneous reading-writing.

• I am looking for advice and best practice for planning the basic level architecture.