Struct ConnSlot 

pub struct ConnSlot {
    pub in_flight: AtomicUsize,
    /* private fields */
}

One slot in the per-DC connection pool.

Each slot is backed by a background sender task (see crate::sender_task::spawn_sender_task), not a locked DcConnection. Enqueueing a request just posts it to the task’s mpsc channel and waits on a oneshot for the result: no lock is held across the network round trip, so any number of callers can have requests in flight on the same slot at once. The task itself batches whatever is pending into as few frames as possible and matches replies back to callers by msg_id, regardless of the order responses arrive in.

in_flight still lets the pool pick the least-busy slot without needing to touch the connection itself.

Fields

in_flight: AtomicUsize