pushpin VS live-cryptocurrency-streaming-flutter

For realtime, I used Pushpin with Server Sent Events. (It supports WebSocket as well).

Instead of letting clients directly interface with your services over websockets, consider using Pushpin [1], which allows you to completely isolate realtime communication from your services.

As a bonus, it also provides you the ability to cycle (redeploy/restart) your services without your clients having to reconnect (that's where the name comes from). And as you can imagine - because communication with your services is entirely stateless it scales like crazy.

[1] https://pushpin.org/

Vapor[0] based on Swift. Advantage of this is that you don't have to evaluate multiple frameworks for Swift and suffer paralysis by analysis. All the Swift community is behind one framework.

The next is Actix[1] based on Rust. There are many frameworks in Rust and most of them have not reached 1.0 And which framework will survive becomes a question.

Other not so well-known is Wt[2] based on C++. This actually is created for programmers who are not web developers. The development experience is similar to desktop app development like Qt.

If that is not acceptable then Django[3], based on Python, is the one that will be good for you.

For the front-end I would recommend Flutter[4]. As much as I dislike getting tied to a single company for whom the framework is not their bread-and-butter, I don't see any other viable options to Flutter that will cover all web, mobile and desktop out of the box.

For databases, I would recommend BedrockDB[5], if you are not averse to SQLite. Or FoundationDB[6], if you want NoSQL. But if you are not concerned about horizontal scalability or okay with self-managing database availability, then PostgreSQL[7] is a very good option.

For push notifications, PushPin[8] is a good option.

[0] https://vapor.codes

[1] https://actix.rs

[2] https://webtoolkit.eu

[3] https://www.djangoproject.com

[4] https://flutter.dev

[5] https://bedrockdb.com

[6] https://www.foundationdb.org

[7] https://postgresql.org

[8] https://pushpin.org

There is also the option of running a proxy which handles the stateful nature of websockets (i.e. https://pushpin.org/), and then handle the rest in a stateless way with lambdas or similar.

This may not be what you are looking for, but why not use a combination of Postgres listen/notify and PushPin[0] to support push notifications?

[0] https://pushpin.org

Could use pushpin[1] and have several fallbacks, like SSE -> Websocket -> polling.

[1]https://pushpin.org/

You can follow the roadmap and request new features directly on Ably Flutter plugin's GitHub repo.