During April 2025, Fillfish focused on backend maintainability across four repositories, including nspcc-dev/neofs-node and redpanda-data/console. He improved code clarity by refining inline comments and standardizing naming conventions, which enhanced readability and reduced onboarding friction for new developers. In filecoin-project/lotus, he updated simulation stage documentation to accurately reflect function names, minimizing confusion during code reviews. For celestiaorg/celestia-app, he corrected documentation typos to ensure technical accuracy. Working primarily in Go, Fillfish applied backend development and code refactoring skills to deliver two features and resolve two documentation bugs, prioritizing long-term maintainability without altering application behavior or performance.