Yes, I also went with the 1st one. Basically the main thread sends a command to an io executor thread, and then waits on the result, which is done using atomic

Yes, I also went with the 1st one. Basically the main thread sends a command to an io executor thread, and then waits on the result, which is done using atomics under the hood. See e.g. https://github.com/cloudpeers/radixdb/blob/sqlite/browser/src/sync_fs.rs#L98 https://github.com/cloudpeers/radixdb/blob/sqlite/browser/sr... Can't wait to play with zaplib. Can you also use it as just a standard library without the GUI part?