What kind of machine do you have? And what is slow, if you upload a lot of stuff or already the web interface?
Caching has a huge impact on performance, for the database, there is a bit of background:
I speed up mine especially for uploads: MySQL analyse tools and performance recommendations - #2 by tflidd
If it is not just slow and you have errors, there is probably something else wrong as well. Framesize buffers errors don’t look good. By the way, NC 15 just went out of support, you should consider upgrading to a supported version (e.g. NC 16). Wait for NC 18 at least for the next point-release.