No Vibes Allowed: Solving Hard Problems in Complex Codebases – Dex Horthy, HumanLayer

Dive deep into the pragmatic world of solving genuinely difficult problems in large, complex codebases with Dex Horthy from HumanLayer. This talk cuts through the hype and vibes-based programming culture to focus on systematic approaches for understanding and modifying legacy code. Learn proven strategies for navigating massive codebases where no single person understands the entire system, including techniques for building mental models, creating architectural diagrams, and identifying critical paths through complex logic. The presentation covers debugging methodologies that work at scale, from distributed tracing and logging strategies to reproducing elusive production bugs in development environments. Understand how to safely refactor legacy code without breaking existing functionality, including writing characterization tests, using feature flags for gradual rollouts, and maintaining backward compatibility. Dex shares real-world war stories of tracking down race conditions, memory leaks, and performance bottlenecks in production systems serving millions of users. Learn about tools and practices that make working with complex codebases manageable: static analysis, dependency graphing, code archaeology techniques using git blame and commit history, and documentation strategies that actually help. The talk addresses organizational challenges like knowledge silos, technical debt prioritization, and convincing stakeholders to invest in code quality improvements. Discover how AI-assisted development tools can help navigate unfamiliar codebases, but also their limitations and when human expertise remains irreplaceable. Essential viewing for senior engineers, technical leads, and anyone maintaining production systems built over many years by multiple teams.