In contrast to direct database access, the HTTP implementation of the abstraction layer performed significantly worse. This will have also been part of the abstraction library having to parse/run the logic as well (nginx + PHP).

From memory, after trying the entire abstraction layer, I boiled it down to as small a file as possible for testing purposes (ie. a single PHP file that took the call and stored it into the DB, no configuration, removing as many "variables" as possible).

EDIT: Direct database access over the network.