A critical bug in our Klarna vendor bundled extension delivered with Magento 2.4.3 and Magento 2.4.3-p1 was identified and an email outreach sent out to all merchants on Magento in September 2021.
The issue is with the size of the Klarna log table. If the table grows beyond the size limit, 32767 entries, it will prevent your checkout from loading. A cron job is set to clean the table regularly, but this mechanism is not working as intended.
To mitigate this issue immediately, you can disable the Klarna logs by setting logging to disabled at Stores -> Settings -> Configuration -> Sales -> Payment Methods -> Klarna -> Configure -> API configuration -> Request Logging.
To fully address the issue in the code, please download and apply the patch. The patch addresses both the issue in the cron job as well as increasing the table size to 4294967295 entries.
To apply the patch, navigate to your Magento root. From your root folder:
We apologize for any inconvenience caused by this, and we are continuously working to ensure stable checkout performance.
If you have any questions, you can drop us a line at firstname.lastname@example.org.