Constant DEFAULT_COALESCE_WAIT_MS 

pub const DEFAULT_COALESCE_WAIT_MS: u64 = 5000;

Default cache.coalescing.wait_ms (DW-038): 5 s — comfortably above a typical upstream fetch so a follower normally out-waits the leader instead of piling its own call on top (the wait bound exists for the pathological leader, not the common one).