Optimize parsers for large datasets

**Description**
Currently handlers lacks proper notifications support.

**Proposed solution**
Add configurable notifications with sensible defaults.

**Priority**: Low/Medium

Start by locating the parser and handler entry points referenced by the title and description. Clarify whether the goal is large-dataset parser optimization or configurable handler notifications, including the notification events and default behavior. Done should include agreed scope and verification that the selected behavior works with representative parser or handler cases.

Written by the indexing model from the issue text.