I'm sure this is on your roadmap but I haven't seen anything public so I thought I'd throw out my use case / thoughts.

I've been experimenting with how to specify the data that needs synced for specific routes in my app. For most apps I can think of building, I'd want to sync all data but it'd be ideal to only load initially the precise data needed for that route and then lazy load other data in the background.

Also I'd want to be able to distinguish between several states a shape can be in i.e. a shape never been synced, it's been synced in the past but while the app has been closed, is stale by 12 hours, and the shape is fully synced up with the backend. Then in my route loader function I could say either wait until fully synced or if the data isn't that stale, immediately render rather than waiting for the initial sync to finish (this has a big impact on the app loading time).

I could imagine a sync manager lib in userland that works similar to this:

      {
        path: `/video/:videoId`,
        element: <Video />,
        loader: async ({ params }) => {
          await syncManager.load([
            {
               shape: () => db.users.sync({ where: { id: params.user_id }}),
               isDone: (shapeMetatdata) => shapeMetadata.msSinceLastSynced < 12 * 60 * 60 * 1000 || shapeMetadata.state === `SYNCED`,
            },
            {
               shape: () => db.youtube_videos.sync({ where: { id: params.video_id }}),
               isDone: (shapeMetatdata) => shapeMetadata.msSinceLastSynced < 12 * 60 * 60 * 1000 || shapeMetadata.state === `SYNCED`,
            },
          ])
          return null
        },
      },

We'd want similar metadata exposed for individual records, especially for tracking individual records e.g. as Bm_Dorian wrote earlier on Discord:

I also have a question. Is it possible to get status if specific record was synced with BE ? Lets say situation: I start up app online, sync and go offline. While offline I insert some records, I would like to show to the user some status of that record that it's not yet on backend. I guess I can achieve that to just save last sync time and compare with time when record was created if still offline, but just wanted to know if there is something for that

or maybe just have boolean field that is when created offline has false value, but on write to backend backend just flips the boolean