Constant SHARED_MEMORY 

pub const SHARED_MEMORY: u32 = 256;

Same-host shared memory over a Unix socket (unix:/path?shm=1, see [crate::shm]): the lease frame carries the mapping and the server’s doorbell page as descriptors, and its parameter is ring u64, the ring’s size. Log sections then go through the ring and durable positions come back in the mapping; everything else stays on the socket. The worker’s heartbeat in the mapping replaces PING. Granted with SHARD_LEASES and SHARED_LOG only.