CREATE TABLE community_serving_write_leases (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    community_id UUID NOT NULL REFERENCES communities(id),
    operation TEXT NOT NULL,
    owner TEXT NOT NULL,
    generation BIGINT NOT NULL DEFAULT 1 CHECK (generation > 0),
    -- Community fence generation observed when this lease was acquired.
    fence_generation BIGINT NOT NULL CHECK (fence_generation >= 0),
    lease_until TIMESTAMPTZ NOT NULL,
    heartbeat_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    created_at TIMESTAMPTZ NOT NULL DEFAULT now()
);
CREATE INDEX community_serving_write_leases_active
    ON community_serving_write_leases (community_id, lease_until);