What hook for triggering an action after saving a new node?
You can use Hook Post Action module which will provide you hooks like:

hook_entity_postsave

hook_entity_postinsert

hook_entity_postupdate

hook_entity_postdelete

hook_node_postsave

hook_node_postinsert

hook_node_postupdate

hook_node_postdelete
These hooks are fired after node is saved to the database. So the process you want to do after node save can be done using these hooks which comes with Hook Post action module.