Refactoring Large-Scale Video Streaming Engineering: Theory and Practice

With the rapid development of video streaming services, the complexity of the business has increased, exposing issues in architecture design, code quality, and engineering capabilities of legacy systems. This has led to a large‑scale refactoring effort.

The article is organized into two parts: a theoretical chapter and a practical chapter, providing a comprehensive overview of the refactoring process.

The theoretical part explains the importance of continuous refactoring, how to design a robust architecture, and how to write clean code, laying a foundation for the practical implementation.

It outlines criteria for deciding whether a project needs refactoring, based on symptoms observed during development, testing, and release phases, such as tangled code, difficulty extending features, excessive bug‑fix time, and lack of automated tests.

Key challenges of refactoring are discussed: efficiency (resource consumption and short time windows), safety (preserving existing behavior and avoiding regressions), and delivery (starting point, handling large codebases, and ensuring sustainable architecture).

To address these challenges, three approaches are proposed: Automation – using IDE‑supported safe refactoring; Systematization – analyzing current architecture, identifying modules and coupling points, and designing a better structure; Engineering – employing architecture guards, static analysis, and unit tests to ensure safety and post‑refactor quality.

The evolution of architecture is presented, moving from monolithic (single module) to componentized, then to plugin‑based, and finally to containerized architectures. Each style’s advantages and drawbacks are summarized.

The article also lists common code smells and bad practices, including mysterious naming, duplicate code, dead code, global/static usage, mutable data structures, overused inheritance, overly long functions or classes, excessive parameter lists, and inappropriate commenting.

For coding standards and static analysis, tools such as Android Studio Lint, ArchUnit, and SonarLint + SonarQube are recommended, with guidance on customizing rules and extending support to other languages.

Design principles and design patterns are mentioned as essential complements to the above practices.

The theoretical chapter concludes with a preview of the upcoming practical part, which will detail the step‑by‑step refactoring workflow, including preparation, code migration, and gradual rollout, scheduled for release on June 14.