Performance problems with many backends or products

Affected version [NIGHTLY-415]

With many products/backends system rapidly slow down. Tested on 1k+ backends and 400+ products.
Also tables with products and backends are very big. There may be used pagination.

Dev Notes

investigate:

• possible missing indexes
• delete warning lists all products/backends
• dashboard pagination

"small quick things" commented in slack:

• fetch the attributes u need only and not the whole objects with all its data even if u r not going to use it.

  .select(...)??
  

• looking for db indexes that might be added to speed things up
• careful also with N+1 queries