If you want to create a custom views access plugin the reason for this will be to allow you to have an entry point to add custom logic to protect the access to your view.
Let say you need a finer access control to a view than roles and permissions. For example you are storing properties on a user object who determine if certain user can see certain views independent of their roles.
What we need to do, is to configure our views correctly with a views access plugin.
When you want to delete a lot of nodes or users you can use the delete all module in drupal. You have some handy drush commands:
drush delete-all article Delect all article nodes.
drush delete-all all Delete nodes of all types.
drush delete-all --reset Delete nodes of all types, and reset node, revision and comment counters.
drush delete-all users Delete users.
--reset Reset counter for node, revision and comment tables.
--roles pick roles
Databases grow even when not a lot of new content is created. What happens is drupal mysql tables start to create overhead, especialy on tables with a lot of deletions. Cache tables, watchdog, access log, variable, ... . Sites that have been running for almost 5 years like this site for example create lots of overhead.
Optimize mysql tables