How inappropriate data access patterns massively slow down programs and how the same problems arise with RESTful APIs.
Retrieving whole rows is hugely wasteful when only part of the row is required to resolve a user request. The issue becomes pronounced when: retrieving sub-parts of the data (projection), consulting multiple tables (joins) or digesting the dataset (aggregation).
RESTful API design consequently suffers the same problems as Active Record ORMs. [...] The largest class of API clients is separated from the server by high latency network links: mobile phones. [...] This means that accessing multiple API endpoints to resolve a single user request can take seconds - an appreciable annoyance to any user.
From ORMs: demand first class queries and transactions. Avoid Active Record style access patterns whether in ORMs or elsewhere.