Optimize helpers for large datasets

**Problem**
When working with store, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

The issue names no file, test, or entry point, so first locate the store implementation and its current error-handling paths. Review existing error messages and tests, then define the specific cases and wording that would count as improved debugging coverage.

Written by the indexing model from the issue text.