Does Flask Session Variable Maintain State Across Threads?

According to the docs: A session basically makes it possible to remember information from one request to another. But elsewhere, the docs say that session is local to a thread

Solution 1:

From the very next sentence after the one you quoted:

The way Flask does this is by using a signed cookie.

Flask stores the information in the cookie before sending the response, and reads it back at the beginning of the next request.