I'd like to start with something that's more DB oriented like SQLite both locally and in the browser for example but I understand a documented-oriented approach might make more sense.
I work on PowerSync and we did a Show HN last year: https://news.ycombinator.com/item?id=38473743
Also see InstantDB Show HN: https://news.ycombinator.com/item?id=41322281
EDIT: actually... it looks like mongo may have just announced the EOL for server-side component a couple weeks ago... bad timing!