[tehlike]

It can eagerload more complex queries.

If you are eagerloading multiple joins relationships, normally that would create a result set of n x m x k x ... rows. With json_agg each relation could be single column in a row etc.

[dmitrytsepelev]

In this case the row size can become huge. Also, how to make sure it's consistent? (I mean foreign keys/unique indexes/etc)

[tehlike]

i was mostly talking about reading side, not mutation side.