kotlinx-datetime VS okio

Kotlin multiplatform types often come with their own serializers. https://github.com/Kotlin/kotlinx-datetime and https://github.com/hfhbd/kotlinx-uuid do, for example.

But we do have such plans for our kotlinx-datetime library and expect to provide at least a partial solution during the course of the year

It depends, time has a complex and native bound legacy. But I bet you want this https://github.com/Kotlin/kotlinx-datetime and DateTimePeriod.

I am involved in the development of Android application which is a rather "thick" mobile client for a Web service. It heavily communicates with the server but also has a lot of inner logic too. So, I decided to use some features of Google Guava library to simplify development process. Here is a list of features I'm very interested in: immutable collections, base utils, collection extensions, functional programming sugar and idioms (common.collect and common.base), primitives utilities (common.primitives), hashing utilities (common.hash), concurrent utils (futures and AsyncFunction). Things I don't want to use in Android: common.cache (see question below), common.eventbus (we have better Android specific libs for this, such as Otto), common.io (we can use okio for Android now).

Yeah Kotlin's own standard library is a lot smaller than Java's currently so you'll need to use something third-party for this. Okio is a popular option https://square.github.io/okio/ it has a Buffer type which is pretty similar to Java's ByteBuffer

Use okio, it is Multiplatform now. I use this for my own library KStore

For networking, file IO, and streams in general, there's Korio and for Java; for just networking, there's LiteNetLib for C#; for what looks like data streams in general, there's Okio also for Java; and Tokio for multi-threaded IO in Rust.

Okio is nice for input/output streams, and sockets.

Sounds like you want https://square.github.io/okio/

On JVM, there is plenty of existing solution already on for multiplatform uses I'd suggest checking amazing Okio library by Square, that seems to cover most of basic use-cases.

I think the main multiplatform library for I/O currently is okio, https://github.com/square/okio. As for compression, you should probably create an expect class for the compressor and use platform specific calls for actual compression. Take a look at https://kotlinlang.org/docs/mpp-connect-to-apis.html.