Twilight is built with a service-minded approach. This means that it caters to both monolithic and multi-serviced applications equally. If you have a very large bot and have a multi-serviced application and feel like Rust is a good language to use for some of your services, then Twilight is a great choice. If you have a small bot and just want to get it going in a monolithic application, then it's also a good choice. It's easy to split off parts of your application into other services as your application grows.
One of the popular design choices when creating a multi-serviced application is to have a service that simply connects shards to the gateway and sends the events to a broker to be processed. As bots grow into hundreds or thousands of shards, multiple instances of the application can be created and clusters - groups of shards - can be managed by each. Twilight is a good choice for this use case: you can receive either events that come in in a loop and send the payloads to the appropriate broker stream, or you can loop over received payloads' bytes to send off.
If you have multiple clusters, then you need to queue and ratelimit your initialized sessions. The Gateway includes a Queue trait which you can implement, and the gateway will submit a request to the queue before starting a session. Twilight comes with a queue that supports sharding and Large Bot sharding, but when you start to have multiple clusters you'll want to implement your own. Our gateway-queue is an example of this.
If you have multiple services or lambda functions that can make HTTP requests, then you'll run into ratelimiting issues. Twilight's HTTP client supports proxying, and can be combined with something like our very own http-proxy to proxy requests and ratelimit them.
You can do so much more than just this, and that's the beauty of the ecosystem: it's flexible enough to do anything you need, and if you find something it can't then we'll fix it. The goal is to remove all limitations on designs and allow you to do what you need.