Constant DEFAULT_KEY_CACHE_CAPACITY

pub const DEFAULT_KEY_CACHE_CAPACITY: usize = _; // 1_048_576usize

The default capacity of the key cache for the relay server.

Sized for 1 million concurrent clients. memory usage will be (32 + 8 + 8 + 8) * 1_000_000 = 56MB on 64 bit, which seems reasonable for a server.