[snaky]

>˜3 times as fast as the nginx-postgresql-c driver

That's interesting..

>LuaJIT FFI is probably the right answer

Do you mean calling nginx internal functions (DB driver or location capture, like ngx_eval module does in that case) via FFI (I doubt if that is safe in any way) or just use libpq from LuaJIT directly?

[xt]

I haven't benchmarked the mysql drivers, so results might be different there.

There's some work being done by openresty author w.r.t. ffi for openresty itself, it might yield interesting results. And yes, I think both the option you listed are viable. But the lua drivers already perform very well.