Hive & Flutter Web - build a database before deploying the website

I am trying to deploy a website which is based on a database to perform operations.

The database is generated starting from assets. My intention is to generate the hive database as a first step and then deploy a website which simply load the hive data previously built. This is crucial as it avoids to re-process the assets again.

Unfortunately, I am not sure this is possible to achieve over the web. In fact, when I write the database and run the application in a single step, everything works (but the website spends time to start because it works on the assets) whereas if I write the database first and run the application in a second step, it appears hive fails to get the content from the boxes. I suspect the database can be generated and managed after the website is deployed not before.

The same app has been developed for mobile. In this environment the above strategy works. The first start up requires more time (the databased is build from the assets) but subsequently, on the next logins, data are loaded in a sec.

Can you confirm me what I am trying to do on the web is not achievable through hive? Or if it is, how it should be done?