Function composite_index_prefix_queries 

pub async fn composite_index_prefix_queries(t: &mut Test) -> Result<()>

Two-column index generates prefix query methods for each valid column prefix (cross-driver).

#[index(game_title, top_score)] generates:

• filter_by_game_title() — partition key only
• filter_by_game_title_and_top_score() — both columns

Verifies both methods issue an indexed operation.