%% @doc What's stored in the database.
%% 'index' is the primary key, 'hash' is also indexed.
-record(plop, {
          index :: non_neg_integer(),           % Primary key.
          hash :: binary(),                     % Hash over mtl.
          mtl :: mtl(),         % Merkle Tree Leaf, an #mtl{}.
          spt_text :: binary() % Signed Plop Timestamp, an #spt_on_wire{}.
         }).