Mike Wille implemented timestamp-based stale peer pruning in the contact book for the nimiq/core-rs-albatross repository, addressing the issue of outdated peer entries and improving network reliability. He designed logic in Rust to filter out stale contacts received via network discovery, ensuring that only recent and valid peers are maintained. To validate the approach, Mike added comprehensive tests that confirmed stale contacts are rejected and that only newer contacts can replace existing ones. His work focused on network programming and robust testing, resulting in a targeted, well-contained feature that enhances the accuracy and efficiency of peer management within the codebase.