The development of an Adobe Commerce website is complete.

Option A is correct because updating the session host value to a shared Redis instance in the “app/etc/env.php” file will allow the session to be saved properly and prevent users from being redirected to the sign-in page after logging in. Redis is a fast and reliable in-memory data store that can be used for session storage in Magento 2. By using a shared Redis instance, the session data can be accessed by any of the backend web servers behind the load balancer, regardless of which server handled the initial request. This ensures that the user’s session is maintained and consistent across different servers1.

Option B is incorrect because increasing the session size with the command config:set system/security/max_session_size_admin will not solve the issue of session not being saved properly. This command only affects the admin session size limit, not the customer session size limit. Moreover, this command does not address the root causeof the issue, which is that the session data is not shared among the backend web servers2.

Option C is incorrect because utilizing the Remote Storage module to synchronize sessions between the servers is not a viable solution for this issue. The Remote Storage module is a feature of Magento Commerce Cloud that allows storing media files and other static content on a remote storage service such as AWS S3 or Azure Blob Storage. This module does not support synchronizing sessions between servers, as sessions are dynamic and transient data that need to be stored in a fast and accessible data store such as Redis3.

References:

1: Use Redis for session storage | Adobe Commerce Developer Guide

2: Security | Adobe Commerce User Guide

3: Remote storage | Adobe Commerce Developer Guide