Redis stores data in memory by default and will lose data on restarts or maintenance unless you attach a volume to your Redis service with a mount path of /data, which allows Redis to persist its RDB/AOF snapshots to disk across restarts.

I have already done this as shown here:

We can see your volume is mounted at /data and Redis is successfully performing background saves to disk. Your current setup is correct, and data written going forward will persist across restarts and maintenance. The data that was previously lost was likely stored before the volume was attached, meaning it existed only in ephemeral storage and was not recoverable once the container restarted. Unfortunately, the previously lost data cannot be restored.