Worked on enhancing query performance in the elixir-ecto/ecto repository by optimizing how exists? queries are executed in Elixir. Focused on database optimization, the approach retained the order_by clause in exists? queries, allowing databases to leverage indexes and generate more efficient query plans. This adjustment removed the previous exclusion of order_by, instead aligning with the select(1) and limit(1) pattern to avoid full table scans and reduce database load, especially on large datasets. Comprehensive tests were updated to ensure consistent behavior across environments, demonstrating a strong understanding of Elixir, query performance, and the nuances of database query planning.