Few questions from reading the docs: 1) How big can all the colocated data for a single primary key get before they don't fit within a split? Can I implement a

Few questions from reading the docs: 1) How big can all the colocated data for a single primary key get before they don't fit within a split? Can I implement a GMail-like product where all the data for a single user resides within one split? 2) Is there a way to turn off external consistency and fall back to serializability? In return you get better write latencies. This is similar to what CockroachDB provides?