Webserver Pico W, logfile management

I have a Raspberry Pi Pico W, which I use to receive data via UART and save it to a log.json file. Using the same Pico W, I also want to create an access point and a web server to display the results. However, I now have the problem that I have two scripts accessing the same file, which leads to conflicts.

I tried using _threads, but it didn’t work due to the versions I’m using. Does anyone have an idea how I could solve this easily? Ultimately, I want the data I receive via UART to be displayed on a web server, and when I refresh the page, the values should also update.

Would be great if someone has an idea or any tips. Thanks! :)