You wouldn’t pull a 100mb database to query in the browser; that’s not how static sites work. Instead, you’d rebuild the relevant pages whenever the content in the DB changes.

Now, for a forum, I’m not sure this is a good idea, unless you have a super fast optimised build process. Even then, the delay in build is not what people expect from a forum. But the OP is not suggesting pulling a 100mb db down into the browser.